Journal of Scientific & Industrial Research

4 scienk ind. Res. "01. 28 No. I Pp. 1-36

January 1969

Published by the Council of Scientific & Industrial Research, Hew Ddhi

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~ ; ..JSIR-JANUARY 1969

Conduction Mechanism in Organic Semiconductors

S. C. DATT

NUMBER I

Plant Sciences in the Service of Man

JANUARY 1969

5

10

ScientificResearch

CONTENTS

Journal of& Industrial

Determination of Force Constants

V. P. S. NAIN & M. L. SHARMA

VOLUME 28

DR ATMA RAM, Director-General,Scientific & Industrial Research(e".officio Chairman), New Delhi

PROF. J. J. CHINOY, Gujarat Uni­versity, Ahmedabad

DR S. DEB, Jadavpur University,Calcutta

DR HARI NARAIN, National Geo·physicalResearch Institute,H yderabad

PROF. N. R. KULOOR, Indian Instituteof Science, Bangalore

DR B. R. NllHAWAN, United NationsIndustrial Development Organization,Vienna

PROF. S. R. PALIT. Indian Associationfor the Cultivation of Science. Calcutta

DR H.A.B.PARPIA,CentraIFoodTech·nological Research Institute, Mysore

DR A. R. VERMA, National PhysicalLaboratory, New Delhi

SHRI A. KRISHNAMURTHI. Chief Editor& ,,,.officio Secretary

EDITORIAL STAFF

EDITORIAL BOARD

Chi.! Edilo,: A. Krishnamurthi

EdilMs: R. N. Sharma & S. S. Saksena

Assistant EdilMs: D. S. Sastry, K.Satyanarayana. K. S. Rangarajan &S. K. Nag

Technical Assistants: A. K. Sen.S. Arunachalam. R. K. Gupta. T. PremKumar. J. Mahadevan & G. N. Sarma

P,oduction OffiCI': S. B. Deshaprabhll

Arc Techniques in the Preparation of Inorganic Materials

R. E. LOEHMAN, C. N. R. RAO, J. M. HONIG &C. E. SMITH

The Applications of Radioisotopes in Metallurgy in India - PresentPosition & Future Potentialities

V. K. IYA

13

17

The Journal of Scienlifle & Industrial R•••archis issued monthly.

The CovncH of Sc.ientific & tn4ultri.1 Re••archUlum.. no responsibility tor the ,tatementsand opinions advanced by contributo,... TheEditorial Board in it. work of examini". pape,..received for publication II ...isted, in an hono­nry clpacity, by ,Iar•• number of di.tinlui,lMidacienti.u warkin&: in various paru of India.

Communication. re••rdinl contributions forpublication in the Journa'. book. for review.subscriptions and advertisements should beaddressed to the Editor, Journal of Scientific "Industrial Research. Publications & InformationDirectorate. Hillside Road, New Delhi 11.

Some Aspects of Carbohydrate Metabolism in Haemoflagellates ...

D. K. GHOSH & A. G. DATTA

Steroid Saponins of Some Indian Plants

R. N. CHAKRAVARTI, (Mrs) D. CHAKRAVARTI,(Miss) SIBANI DATTA & M. N. MITRA

Reviews ...

The Philosophy of Quantum Mechanics; Semimicro Ql1alitative AnalysisjMedicinal Plants; Animal Gametes (Female)

22

26

28

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Notes & News

Lasers for measuring rates of ultra.-fast ~hemieal reactionsj Melting point.determination by NMR; A new synthesis of ~romatic and aliphatic carboxylicacids; A new oxytocic substance from ox hypothalamus; Quantitative analysisof S-adenosylhomocysteine in liver; A Dew method for the detennination ofblood volumej Progress in leprosy research; Regional Research Laboratory,JaDlIDu; Pasteur Institute, Coonoor; Inlernatio'fQl Journal of Soil Biology andBio&hemislry; 1'echnological Foreoa.stiHgj Journal of Noncrystalline Solids; NewPeriodicals from Pergamon Press Ltd; Forthcoming International ScientiftcConferences, 1969

32

© 1969 THE •COUNCIL OF SCIENTIFIC &INDUSTRIAL RESEARCH. NEW DELHI

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ISIR-JANUARY 1969 A9

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FLUIDIZATION AND RELATED PROCESSES

A Symposium

Held under the auspices of the Chemical Research Committee at theIndian Institute of Technology, Kharagpur. 6-7 January 1964

Contains twenty-seven papers distributed under five sections: (i) Fundamental Measu re­ments (2 papers), (ii) Physical Interpretation and Momentum Transfer (9 papers). (iii) MassTransfer in Fluidized Beds (3 papers). (iV) Heat Transfer in Fluidized Beds (5 papers) and(v) Chemical Reactions in Fluidized Beds (8 papers).

Pages xii+272, Royal 8vo, Rexine bound

*

Price Rs 24.00, Sh. 48.00. $ 8.00

INDIAN FOSSIL PTERIDOPHYTESby

K. R. SURANGEDirector. Birbal Sahni Institute of Palaeobotany. Lucknow

All available information on Indian fossil pteridophytes has been brought together in this

compilation. It deals in detail with descriptions and taxonomy of fossils. Useful for

students, teachers and research workers in palaeobotany.

Pages viii+210, Royal 8vo

Copies available from

Price Rs 23.00, Sh.46, $ 8.00

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Plant Sciences In the Service of Man*

I N the world of today" it is not necessary to dwellupon the importance of science in the life ofa nation. Even the most primitive societies

have started thinking about improving scienceeducation and the training of scientists. The verysurvival of developing countries today dependson adequate' acquisition of scientific and technicalknowledge and its full utilizatIOn in agriculture,industry, defence and other spheres. This has beenbrought out very clearly in the Science PolicyResolution of the Government of India adoptedin 1958.

Around the beginning of the 17th century, whenscience was just entering upon its modern phaseof active growth, Bacon listed what could be ex­pected from science. His important expectationsfrom science were the prolongation of life, therestitution of youth in some degree, the curing ofdiseases counted incurable, the mitigation of pain,the increasing of strength, the altering of consti­tution such as fatness, leanness and stature, makingof new species, making better instruments of des­truction for war, exhilaration of the spirits andputting them in good disposition, increasing theforce of the imagination either upon another bodyor upon the body itself, acceleration of putrefac­tion and germination, making rich composts for theearth, making of new food out of substances notnow in use, making new threads for apparel, etc.

While some of Bacon's notions are not sharedby modern science and a few of his expectationsare still not realized, it is obvious that we haveachieved today almost everything that he desiredand many things more. Bacon, for example, neverimagined utilization of mechanical power, electri­city, nuclear energy, acceleration of' transport andcommunications, television, space travel; etc, whichare common things at present. His major interestwas in problems of health, freedom from commonailments and prolongation of life. The realizationof all these expectations, nearly 250 years old, hasnot, however, solved the problems of mankind.The progress of science in one field has creatednew problems in another. Thus the advances inmedical sciences have greatly increased the ex­pectation of life. In advanced countries a newlyborn child expects to live now to the age of 75-80years. Even in India the application of simplehealth measures in two decades since independencehas resulted in nearly doubling the longevity from27 to 53 years and the average male in Punjab ex­pects to live for 60 years. The result has been a, population explosion' unprecedented in history andmankind is faced with the grim possibility of dyingfrom famine and starvation instead of disease.

• Address of Dr A. C. Joshi, General President, Fifty­sixth Session of the Indian Science Congress, Bombay,3 January 1969.

The condition of many underdeveloped Asiancountries, India, Pakistan, Indonesia, Philippines,China, etc, where civilization developed earlierthan in other parts of the globe and which arealready over-populated, is particularly precarious.Feeding their poor and malnourished millions hasbecome a source of much anxiety to their govern­ments. Foodgrains have had to be imported fromoutside in large quantities. Many experts forecastthe occurrence of widespread famine in the earlyseventies.

During the last five years, however, a silent re­volution has t,\ken place in these countries throughwhat has become known as the modem agriculturaltechnology. This implies the use of high yieldingdwarf varieties (wheat and rice), hybrid vigour(maize, jowar and bajra), dependable irrigation,fertilizers, pesticides and fungicides, better machi­nery and electric power. In 1967, world agricul­tural production set a new record and the under­developed countries accounted for most of thatincrease. The agricultural output in these countriesrose by 7-8% over 1966. Per capita food productionincreased by 6%.

In Indian economic history also, 1967-68 is oneof the most significant years. Ninety-five milliontons of foodgrains were harvested. More than15 million tons of wheat alone were harvested.This is more than double the production of 1951.In, a few years, India aspires to be self-sufficientin foodgrains and even hopes to export some rice.The Philippines, which has been importing foodin large quantities for many years, harvested arecord rice crop in 1967 with only 14% of its rice­fields planted with the new 'miracle variety' IR8.It even exported some rice. Similarly, Pakistanharvested 5·5 million tons of wheat and it has goodchances of achieving self-sufficiency in foodgrainsin another year and is looking forward to an exportpotential in the Fourth Five Year Plan beginningfrom 1970. The first sproutings of the 'greenrevolution' have naturally generated all-round hope.We can say positively that many countries whichwere faced just a few years ago with the prospectsof a large-scale famine are today on the brink ofan unprecedented opportunity. The critical foodproblem of the next 20 years can be solved withknown agricultural techniques.

If the present pattern of consumption continues,the foodgrain requirements of India by 1975-76are expected to be 150 million tons. These willrise to 200 million tons by 1985. Both these tar­gets are within reach by extending the cultivationof high yielding varieties already avai labIe ill thecountry or likely to be produced at the plant-breedingstations in the near future and by providing therequisite inputs of water, fertilizers, etc. The taskbefore the plant scientists now is to explore the

J. SCIENT. IND. RES., VOL. 28, JANUARY 1969

means of meeting the food requirements after 1985and at the end of the century, as even with the fullapplication of the known agricultural technology,people will outstrip even an expanded food supply.

The food problem could be solved if the worldwere to achieve a stable popUlation in 20 or even30 years. This is, however, not likely to happen.The average rate of population growth at presentis about 2·5%. In large areas of the underdeve­loped world the population growth is likely to shootup to 3'5% as soon as essential health services areorganized. Despite the fact that very determinedefforts are being made in many countries to limitthe size of families, the population is going to touchthe 6 billion mark much before the end of thecentury. Whether it shall be stabilized by theend of the century is an open question. It willbe hazardous to base plans of food production onsuch an assumption. We should be only too wellaware of the fact that the extinction of many domi­nant species in the past has followed the explosionof population. Man by his skill has survived aseries of such population explosions in the pastfollowing pastoral, agricultural and industrial phasesof his cultural evolution. He can survive the pre­sent crisis of scientific revolution due to the pro­gress in medicine by control of his environmentand the proper planning of food production wellahead of his requirements. If the world is in aposition to feed its population today, it is due tothe basic discoveries made in plant sciences, thatunderlie agriculture, during the last 40 years.Planned scientific studies to feed a population of6 billions or more at the end of the century mustbegin now.

While it may become possible to manufacturecarbohydrates and other simple food materials indue course with the help of atomic energy or othersources of power without the aid of plants, onecannot hope much from such sources to feed themillions. Mankind will continue to depend for along time for food largely on solar energy capturedby the green plants.

Further, our efforts to utilize unconventionalfood, from Chlorella to wild tree leaves, thoughpossible, pose formidable technological problems.Recent work of Odum and others has shown thatthe seas and the oceans are not so productive asthey were once considered, since the holding of largeproteinaceous biomass is no guarantee for sustainedhigh rate of production. Indeed, they have beencompared with deserts in the matter of rate of pro­duction among the terrestrial ecosystems.

Technically, it is possible to argue that land maybe better utilized if we were to obtain our foodresources largely from selected trees than fromcereals. It is also sometimes said that the climateof tropical countries is better suited for' tree culture'rather than for 'grass culture '. The argumentruns like this: all materials used for food by manultimately come from green plants which grow byutilizing the energy of the sunlight. Even the bestfarmlands use annually only a fraction of the solarenergy that falls on them. Assuming the averageannual input of solar energy for India as about200 kcaljcm2 and allowing for reflection from and

2

transmittance through the leaf of about 25% ofthe only 50% as photosynthesizable light energy,we get a figure of 12% of energy fixation on thebasis of 10 quanta being used per CO2 molecule.Roughly 25% of the fixed energy is used up in res­piration, leaving only 9% of the fixed energy forgrowth of just 18 kcal of the input of 200 kcaljcm2

for the whole year provided the land is covered withleaf all the time. However, in actual practice theaverage yield of paddy and wheat in India is 1 tonper hectare or roughly 0·01 g(cm2 which corres­ponds to about 0·04 kcal of fixed energy per cm2

(1 g plant tissue being equivalent to 4 kcal of energy).Trebling this figure to 0·12 kcal(cm2 may give usa rough estimate of the total energy fixed duringthe growth of the whole plant during a season. Ifwe raise two crops in a year, the annual yield canbe 0·24 kcal of fixed energy per cm2 against thepotential of 18 kcal. The gap between the poten­tial and realized values is staggering. The dif­ference is mainly on account of light satnration ofthe photosynthetic apparatus so that most of thebright light during the day is not used. Never­theless, it has been possible to raise plants whichreach light saturation in more intense light. Therate of organic production in our forests has beenshown to be of a higher order than achieved so farby any cereal, and possibly in trees the critical lightsaturation intensity is of higher order. Further,the wild vegetation does not need manuring, irriga­tion and labour input necessary for raising a crop.This is possible on account of the dynamic equi­librium of flow of energy and cycling of minerals inthe natural ecosystem. It is said that man hasonly to learn the technology of extracting food fromthe wild vegetation in order to be free from thetedium of agriculture.

In spite of the higher productivity of the forests,it is not likely that men will change their food habitsso drastically as to obtain the greater part of theirenergy requirements from trees. Conventionalagriculture would continue to be the mainstay offood requirements of the people and the problembefore our country as well as before other parts ofthe world is how to augment food production throughconventional agriculture on a decreasing area offarmland·.

In the ECAFE region, during the period 1960-66,the average foodgrain output increased at the rateof 1·1 % against 2·5% increase in the population.In India agricultural production increased at therate of 3·1 % against a rise in demand of 3·36%during the same period. The gap between foodrequirements and food output has been met bylarge-scale imports from outside. The heavyimports during the past years have affected veryadversely our plans of economic development.Further, we are not sure whether foodgrains will

'We have no exact data for our country but it hasbeen estimated that in the United States about one millionacres of land are consumed every year by growing cities,suburbs, factories, roads, airports, etc. It is estimated thatnearly one-tenth of the farmland will be used up in thismanner in the next 40 years during which period thepopulation will double itself. A similar situation may arisein India as we take to large-scale industrialization. housingof the ill-housed people. provision of roads, etc.

PLANT SCIENCES IN THE SERVICE OF MAN

be available for us from other countries in the future.The food surpluses in USA are rapidly dwindling.All the production there may be required to meetits own growing population. Every country, unlessit is heavily industrialized like Japan or GreatBritain, would have to meet its food requirementslargely by increasing production from its own fields.

Thus in most countries, two curves, one for de­creasing farmland and the other of rising population,are on a collision course. The security of man liesonly if new advances in plant sciences result insufficient increase in productivity as to stave offthis collision.

Fortunately, very rapid progress is being madein different branches of biology since World War II.Many thoughtful people have even begun to regardthe second half of the 20th century as the commence­ment of the 'Age of Biology'. We are betteraware now about the nature and diversities of life.The discoveries in botany are opening up entirelynew vistas in our understanding of plants. Someof these findings are as important as the great dis­coveries in physics that have led to the tappingof nuclear energy.

When one attempts to classify these develop­ments, it is seen that some of them are at presentof a purely theoretical interest and have no directbearing on agriculture. They greatly broaden,however, our knowledge of plant life. In this cate­gory can be placed the discovery of algae-like andbacteria-like fossils from pre-Cambrian rocks, whichput back the origin of living organisms on the earthto about 3 billion years, that is almost a billion yearsearlier than was considered likely only a decadebefore. Another such example of great interestis the development of new biochemical techniquesfor characterizing and making visible the fineststructures of the cells down to individual largemolecules.

Other recent discoveries are of immediate practicalvalue and hold out promise of revolutionary appli­cations to agriculture and food technology. Themost important among them are concerned withthe understanding of the precise nature and thesubtleties of heredity. As a result, the long­cherished goal of producing varieties of crops toexact specifications is now coming into view. Thisis making possible the production of many greatlyimproved strains.

A good example is the recent development ofhigh yielding varieties of dwarf wheats. Scientificimprovement of this cereal in India was startedsome 50 years ago at the Indian (then Imperial)Agricultural Research Institute. Eight years agoa critical study of factors responsible for the yieldstagnation as well as instability in the productionof this crop was made. It was concluded that themorphology and the developmental rhythm of thetall varieties cultivated in the country until then-were not conducive to the production of wheatunder conditions of high soil fertility and irrigation.The tall straw made the crop liable to lodging when3-4 months old. Further, many of the commonvarieties were susceptible to rust and smuts. When­ever the farmers gave more irrigation and fertilizers,the intensity of attacks of rust and smuts increased.

In addition, in Northern India, rains and hailstorms,which are frequent in late March and early April,caused the lodging of the crop even under condi­tions of poor fertility. The analysis of this kindled the workers at the Indian Agricultural ResearchInstitute in 1962 to the conclusion that dwarf wheatvarieties were essential for breaking barriers tohigh yields in irrigated fields. A request was madeto the Rockefeller Eoundation for the seeds of thedwarf wheats already developed in Mexico. In1963, after visiting the wheat-growing regions ofthe country, Dr N. E. Borlaug sent 100 kg eachof 4 dwarf and semi-dwarf wheat varieties and smallsamples of 613 promising selections. The seedswere grown and the crops studied at Delhi, Ludhiana,Pusa, Kanpur, Pant Nagar, etc. In 1964, it wasfound that the Mexican varieties Lerma Raja andSonora 64 yielded over 4 tonnes per hectare atseveral places. Seeds were multiplied during sum­mer months in the Nilgiri Hills in South India.During the rabi season, the dwarf wheats weretested at 155 locations and subjected to detailedpathological, physiological, agronomic and qualityevaluation. In 1965, the results from yield trialsconducted all over the country led to the releaseof Lerma Rojo and Sonora 64 for general cultivation.The yields obtained by farmers were so encouragingthat it was decided in 1966 to import 18 thousandtonnes of seeds of Lerma Raja and a few othervarieties from Mexico. These were sown in 400,000hectares during rabi season, along with the recom­mended doses of inputs, under the High YieldingVarieties Programme. In 1967, these dwarf wheatswere cultivated in nearly 2 million hectares andthus started the great agricultural revolution inthe country. Such rapid spread of new varietieshas not been paralleled anywhere in the world. Inthe summer of 1968 nearly 17 million tonnes ofwheat were harvested in the country as against theprevious best of 12 million tonnes.

An amber-seeded mutant developed at the IARIby treating Sonora 64 with gamma rays and releasedunder the name of Sharbati Sonora deserves specialmention for its high protein content. Its yieldshave touched more than 6 tonnes per hectare. Itpossesses on an average 16'5% protein in contrastto about 14% in Sonora 64. Further, this varietyhas about 3 g of lysine in 100 g protein in contrastto about 2·4 g in Sonora 64. The mutant has helpedto establish that protein quantity and quality inwheat can also be improved simultaneously withincreasing yields. As the Indian diet is generallydeficient in proteins, this discovery is of great signi­ficance in improving the nutrition of the masses.It also holds much promise for the future in develop­ing high yielding as well as high quality crops.

The wheat revolution has helped to bring abouta great change in the outlook and agronomic practicesof farmers because new varieties can assist in doub­ling the yield and income. The farmers havebecome aware of the need for several fundamen­tal changes with regard to the time and methodof sowing and in the timing of irrigation andharvesting.

The recent developments in plant physiologyare as revolutionary as those in the field of genetics.

3

J. SCIENT. IND. RES., VOL. 28, JANUARY 1969

The investigations on the different types of planthormones - auxin, gibberellin and kinetin - aregiving us new ideas about the growth and develop­ment. The basic studies on the auxins have ledto the development of chemical weed killers. Thediscovery will save not only a good deal of back­breaking labour, but it will also greatly augmentthe yields of crops.

Rapid advances are being made with regard tothe understanding of the influence of both internaland external environment on flowering. This hasled, among other things, to the discovery of a newlight-detecting pigment in plants, the phytochrome.These studies make it possible to have a precisecontrol of the time of flowering of crops by chemicalsprays or by exactly timed artificial illumination.Thi~ opens up the possibility of industrializationof agriculture, particularly of greenhouse cwps.

Then there are discoveries about the occurrenceand functions of the trace clements in soils - zinc,copper, boron, manganese, cobalt and molybdenum.These findings have helped to explain many pro­blems of plant nutrition and hold out the possibilityof bringing large areas of wasteland under fruitfulcultivation.

The cultivation of isolated fragments and evensingle cells of plants marks a new advance on thevery old problems of plant differentiation and organo­genesis, namely how different tissues and organscan be formed from cells with the same heredity.The growth of whole plants from single cells hasalso many practical applications and hclds outrevolutionary possibilities in plant propagation.

There is a growing understanding of the masterrole of the nucleic acids in controlling growth, dif­ferentiation, pigment formation, etc. Then we haveDOW a much clearer picture of photosynthesis, theascent of sap and the translocation of nutritiveelements, the chemistry of synthesis and breakdownof many of the major metabolites, the differentkinds of enzymes, etc. These advances are enablingus to understand more fully many of the mysteriesof plant life. While this knowledge is of funda­mental importance for its own sake, it will in duecourse have practical applications in agriculture.

The mysteries of the biochemical reactions whichlead to the fixation of nitrogen from the air havebeen gradually unravelled. These discoveries mayopen the way to vast new nitrogen fertilizer re­sources.

There are many questions about the nature ofthe plant world about which we still know verylittle. How is it, for example, that the green plantscan manufacture from 16 elements an enormouslycomplex series of organic compounds including,besides carbohydrates, fats and proteins, a varietyof vitamins, many toxins, stimulants, drugs, ,scents,pigments, fibres, etc? What determines the se­quenc,e of germination, growth, maturity, fruitingand ageing of plants? How is it that the sea waterkills most land plants if used for irrigation, whereasthousands of species of plants, including someflowering plants, live in the sea? Why different

4

species grow in specific habitats? Why certainplant~ c~not stand even slight frost, while otherscan lIve m subarctic conditions? It will take aI<:mg time before answers are found to these ques­tions, but what has been learnt already in recentyears holds out great promise for the future.

The application of the recent discoveries in dif­ferent fields ~f plant science opens up vast possibi­lities of obtaming higher yields from the cereals aswell as ot~er crops several times the present levelof prod':lctlon. In order to derive full advantagefrom thIS knowledge very sustained efforts to im­prove biolog;ical and agricultural education, research~nd exten~l~n are essential. The great increasem productiVIty in the United States during thel~st 40 years IS mamly due to a highly developedbIOlogy and productive agricultural practices. Ina count~y hke ours, where agriculture is much lessproductive, the need to improve the study of andresearch in biological sciences is urgent. Therehas also to be created a climate of science in thecountry. Adjustments have to be made in land­use and cropping patterns. Irrigation facilitiesand rural electrification on a large scale have tobe proVIded. Fertilizer production has to be greatlystepped up. Pesticides and fungicides have to bemad.e easl.ly ~vailable. Machines for quick har­vesting, SCIentific storage and roads to villages have~o be provided. Animal husbandry has to be greatlyImproved, keeping in view the fact that the cattle~omP~te directly with man for food, that they aremefficlent converters of energy and increase in theirp.opulation is likely to deplete the primary produc­tIon, but they have the capacity to digest the fibrousconstituents of plants which otherwise are uselessto man. Finally, all-out efforts are required toactivate the vast population to the problems thatit is facing, their possible solution, and to improvingthe farmer's ability. All this must be done withoutdelay. We should not imagine that the food pro­blem has been solved. It is going to be continuouslywith us and will need our earnest attention all thetime.

Fortunately, man's position in the biosphere isunique. He has the capacity to manipulate thephysical and biological environment to his advan­tage. His cultural revolution holds great promiseprovided he is conscious of his limitations, and plansto overcome them in good time. The remainingpart of the century places him in a precarious posi­tion. Food production is undoubtedly increasing,but the population is growing as fast if not faster.Hence special efforts are required in developingcountries to boost up agriculture in the hope thatboth food and population growth shall becomestabilized by the turn of the century. This briefperiod may be regarded as a breathing spell in therace for man's survival. If he utilizes the opportu­nity wisely to his full advantage, making use ofthe scientific method and the technology that sciencehas given him, he would overcome the present crisisof exploding population as he had overcome severalother catastrophes in the past.

Conduction Mechanism in Organic SemiconductorsS. C. DATI

Department of Physics, Government Science & M.H. College of Home Science, Napier Town. ]abalpur

... (5)

... (3)

...(4)

...(1)

temperature activation energy seems to be relativelyinsensitive to the purity of the material. Hence. thehigh temperature activation energy is a characteristicproperty of the material and not a function ofsample purity and can. thus. serve as a reliableparameter for comparison with other solids.

Comparison with Inor~anic SemiconductorsAlthough more than 800.000 organic compounds

have been characterized. the electrical conduCtivitiesof only a very small number have been studiedl-17.The major portion of the information on organicsemiconductors of molecular crystal type publishedup to the middle of 1966 has been given by Dattet al lO • The present paper is devoted completelyto molecular crystals for three reasons. First. physi­cists are interested mainly in crystalline materials;secondly. maximum number of investigations havebeen carried out on the semiconductive properties ofmolecular crystals; and lastly, the shortage of spacein the present paper does not permit the discussionof the other two types of organic semiconductors.ie charge-transfer complexes and polymers.

In the case of organic semiconductors of themolecular crystal type. it has been found thatplots of log a against the reciprocal of the absolutetemperature yield one or two intersecting straightlines. This suggests a relationship between electricalconductivity a and absolute temperature T of theform

a = aD exp (-E/kT)

where the symbols have their usual meanings.From the formal similarity between this and theequation for the electrical conductivity of an intrinsicinorganic covalent semiconductors (eg germaniumor silicon) the quantities in Eq (1) can be interpretedin terms of the model underlying Eq (2):

a = aD exp (-</2kT) ... (2)

ie any conductivity is assumed to be intrinsic. sincethe material has been prepared as pure as possible.These model parameters are the effective mass m*of the charge carriers. their mobility II and con­centration n. They are defined as follows:

a = nell

[2(27tm*kT)3/ 2] exp (-</2hT)n = k3

and

k 2

m*=~

47t2

dK'

where h is Planck's constant; E', the energyassociated with the wave vector K; K = 27t/>"; and>., the de Broglie wavelength of the electron.

THERE has been considerable interest latelyin the electrical conductivity of organicsemiconductors1'8. Recently. Datt et allO

have discussed. the various aspects of this interestingsubject. The subject is interesting because thenature of charge transport in these materials is dif­ferent in many important respects from that of con­ventional elemental and compound semiconductors.The theoretical understanding of electronic transportprocesses in organic semiconductors is a problemcomplicated by many subtle, interrelated effects.This diffiyulty still persists even if the discussion isrestricted to the mechanism underlying the mobilityof charge carriers in an applied electric field. therebyeliminating discussion of the processes of charge­carrier formation. recombination, trapping and otherpractical difficulties which exist in the total transportproblem.

Experimental FactsAny theory describing the process of electrical

conduction in organic semiconductors must adequate­ly account for the following experimental facts:

(i) The electrical conductivity can usually be fittedto an equation of the form a = aD exp (-E/kT)'where a is the electrical conductivity; aD is aconstant; E. the activation energy; k. the Boltzmanncon tant; and T. the abSOlute temperature. Theactivation energy E is found to be generally of theorder of a few electron volts.

(ii) For some materials. ie naphthalene1o-12 andanthracene10•13• a considerable anisotropy exists. sothat conduction in a direction perpendicular to thecleavage plane is notably smaller than within anydirection in the cleavage plane. For other materials.the anisotropy effect appears to be either muchsmaller or completely absent. The activation energyE is found to be independent of the crystalorientation within experimental errorllH3.

(iii) The dark current is found to be ohmicup to the field strengths of 1500 V/cm (ref 1-15).Above this field strength the current increases at amore than linear rate. These trends in the variationof current with f\eld strength arc irrespective of thesample purity11. The conductivities measured nearroom temperatures are very low (a = 10-7-10-18 ohm'lcm-l or even less). They change very little uponfusion. although exceptions do occur. as in the caseof naphthalene10,I6,I7 and anthracene10,17.

(i v) Though the effect of impurities has not beeninvestigated very systematically by most of theauthors. it appears that they ~ffect both dark andphoto-conductionl-1o. The studies of Dattll• Nor­throp and Simpson14 and Gravatt and Grossl6 onsome organic semiconductors are significant in thisdirection. These studies conclusively show that thepurity of the material has a marked effect on themagnitude of the electrical conductivity and on thelow temperature activation energy. but the high

:;

J. SCIENT. IND. RES., VOL. 28, JANUARY 1969

The three assumptions implied in substitutingEq (2) for the experimentally obtained Eq (1) are:(i) the energies of the electrons in the solid can bedescribed in terms of the two-dimensional analogueof a system of Brillouin zones; ie by definite energybands separated by a forbidden zone; (ii) since thebasic excitation process in intrinsic conductioninvolves the generation of an electron-hole pair, itmust be assumed that one type of carrier becomestrapped in order to explain the experimental factthat organic semiconductors are either p- or n-type(in fact, most are p-type, ie they conduct by meansof positively charged electr~m vacancies) ; and (iii) theenergy of an electron is a parabolic function of thewave vector K.

The mobility will depend on certain details of themodel employed. The material is, therefore, assumedto be an intrinsic conductor and scattering of thecharge carriers due to impurities must be negligible,leaving only scattering by the lattice and by dis­locations and other structural faults to limit mobi­lity. Since only a few organic semiconductors canbe obtained in the form of single crystals, thelatter mode of scattering would be expected topredominate. However, in view of the irregular­ities necessarily involved in such crystal imperfec­tions, no reliable calculations which are valid fora compacted powder or a cast pellet have beenpublished.

The mobility contribution due to dislocations alonehas been computed by Dexter and Seitzl8 ; if latticescattering alone limits mobility then the 'mobilityshould be proportional to m*-5/2 T-3/2. Thus, in viewof the exponential factor in Eq (2), it is furtherimplied that the mobility varies relatively littlewith temperature and that any such variationwould be compensated by the T3/2 term in Eq (4)which determines the concentrations of chargecarriers.

The above approach which is based on theassumption that the organic materials are intrinsicsemiconductors obeying the same laws as theinorganic intrinsic semiconductors is not universallyacceptedl ,l9. According to Garett l and Foxl9 there isinsufficient justification at present for making such anassumption and even if the organics are intrinsicsemiconductors, it is possible to show that the factorof ! should not appear in the exponent. The factorof ! in the exponent in the case of an inorganicintrinsic semiconductor appears because the possibledistributions of electrons in the conduction band areindependent of the distributions of holes in thevalence band. This factor appears also in the caseof an equilibrium distribution of ion pairs. However,in molecular excitations, once one determines adistribution of electrons among the excited statesof the various molecules, the distribution of •holes'in the ground state is completely determined. Insuch a case the factor of ! does not appear. Theseconclusions are based on general statistical argu­ments, not restricted to solids. It is required onlythat the Fermi level be far, compared to kT, fromany of the one-electron states. Hence, a seriousdoubt is thrown upon the efforts to correlate 2Ewith' energy gaps' determined by optical methodssuch as absorption or phosphorescence. This has

6

been shown theoretically and experimentally by someworkers1,ll,tO. In addition, Matt and Gurney21 havepointed out that, because of the Franck-Condonprinciple, thermal and optical activation energiesshould not be expected to agree.

Band Structure in Molecular CrystalsEven if a purity sufficiently high to ensure intrinsic

conductivity can be achieved, it is highly question­able to what extent a model based on studies ofcovalent crystals like germanium or silicon can besafely extrapolated for organic materials in thecrystalline, glass or liquid form. It has been shownby Ioffe and Regel22,~ that serious contradictionsarise when the low values of mobility Obtained formost organic semiconductors are considered. Acarrier of effective mass m* and mobility fL, atordinary temperatures, has a mean free path Lgiven by the approximate relation22 :

L~lo-8 fL(,~J ... (6)

where mo is the mass of the free electron. Values ofL lie between 0·1 and 10' A. Consider a free electronor hole moving with thermal velocity at ordinarytemperatures. Since its de Broglie wavelength .\ isof the order of 70 A, it appears that L becomesless than .\ if the mobility drops below about100 cm2JV-sec. However, as an electron is • smearedout' over distances of the order of .\, a motionover a distance L less than .\ becomes meaningless.Moreover, most organic substances have values ofmobility less than 5 cm2/V-sec so that the meanfree path L, calculated from mobility data, is of theorder of 0·1-1 A; this value is appreciably lessthan the lattice spacing in a molecular crystal.Therefore, neither the concept of a mean free pathnor that of a free electron mobility has any meaningin such a case, since the electron wave is com­pletely damped out within less than a single latticespacing.

Further difficulties arise if the change in conducti­vity upon melting is considered. If lattice scatteringwere indeed the rate-determining step, then a changein the conductivity similar to that observed in thecase of metals would be expected. Most metalsobey, at least approximately, the Mott2&-Harasima26

relation

O'solid = exp (-2Lf I3Tf) ... (7)aUquid

where Lf is ,the latent heat of fusion per molecule orper atom, and 1f the melting point; numericallythis ratio is about 2 for most metals, The loss oflong-range order on melting, however, has even lessinfluence on the conductivity of organic semi­conductors than it has on metals where latticescattering is the main mode of scattering, It hasbeen shownl6,l? that, though conductivity increasesby some orders on melting, there is no change in theslope of the log 0' versus liT curve on melting.Hence, it may be assumed that melting only raisesthe mobility to a higher value in the liquid state butleaves the band structure of the organic substanceunaltered.

DATT: CONDUCTION MECHANISM IN ORGANIC SEMICONDUCTORS

Therefore, it appears that the band structurearises not because of long-range order, but rather isdetermined by the chemical bonding, the type ofcoordination and the type of short-range order inthe substance, and is thus preserved upon melting.Long-range periodicity may be a sufficient but isnot a necessary condition for the development ofenergy bands. The concept of a conduction bandseparated from a valency band by a definite energygap may, therefore, be applied to a molecular crystal.On this basis, it has been shown by Gubanov28

that the width of the gap remains substantiallyunaltered if a crystal having long-range order meltsinto an amorphous liquid or glass having onlyshort-range order, provided that the coordinationnumber remains unchanged. The following expres­sion for the conductivities in the solid and liquidstates can be derived21 :

uso);d = iLsolid exp (tl./2kT) ... (8)O'liquid !J.liquid

where tl. is the change of the .energy gap uponfusion. Since tl. is small, the value of the fractionalso becomes small and in the limit approaches themobility ratio.

MOblllty Problem andConduction Mechanism

It is clear that mobility as such has little meaningin the case of organic semiconductors where inter­molecular distances are of the order of severalAngstroms. The very existence of organic semi­conductors, however, shows that some means ofcharge transfer must exist to permit an electron orhole to migrate from one molecule to another.Whatever the nature of this process, it must be avery improbable event since the conductivity valuesare small.

The distinguishing feature of the organic semi­conductors is their narrow bandwidths; specifically,bandwidths <kT" where k is the Boltzmannconstant and- T, the room temperature. As aconsequence of the small overlaps, it is not evidenta priori that a conventional energy band modeland Boltzmann equation treatment are applicable indescribing their transport properties. It has beenshown28 that in semiconductors of sufficiently narrowbandwidths, for which the electron-lattice interactionis sufficiently strong, the latter must, in effect, betaken into account before the periodic potential,giving rise to the so-called small polaron mechanismof charge transport. For this case at sufficientlyhigh temperatures, a band model is found not toapply. Rather, the transport mechanism is athermally activated29 ,30 hopping motion of the chargecarrier between neighbouring lattice sites in whichthe interaction of the carrier with the lattice playsan essential role.

rt is, therefore, somewhat surprising that there isno experimental evidence of the above mechanismin the commonly studied organic molecular crystals,ie anthracene and naphthalene. Thus, althoughthe electrical conductivitv follows the standardsemiconductor Eq (1), the-temperature dependenceof the mobility, as deduced from transit time81,32 andHall measurements33, varies typically like IJ-""T"',

where 3~n~ 1. In particular, there is no evidencethat the mobilities have an activation-type tem­perature dependence.

Band ModelOne line of attack on the conduction problem in

molecular crystals was started by LeBland14, whonoted that electron and hole mobilities increase withdecreasing temperature31 in a manner not unlike thatto be expected from a band theory model. Chargetransport by phonon-assisted hopping from one siteto another would, on the other hand, result in anexponential increase of mobility with increasingtemperature. This observation led LeBlanc andothers to treat the conduction problem within thetight-binding approximation of the band theory:w.-38.

Intermolecular overlap integrals for anthracene werecalculated first by MurreI3? Later calculations ofthis type are provided by Thaxton et al3s , andRice et ap8,as,3s for anthracene and naphthalenecrystals, which have base-centred monoclinic crystalstructure. Except for variations in the estimatesof the intermolecular transfer integrals among theabove workers, this aspect of the problem is relativelysimple due to the simplicity of the tight-bindingapproximation. This theoretical work has indicatedthat the bandwidths for excess electrons and holes inmolecular crystals of the naphthalene-anthracenetype are very narrow, 0·2 eV at the largest, andpossibly smaller than that by an order of magnitudeor more.

The more difficult problem within the bandapproximation is a proper treatment of the scatter­ing. Most of the workers35 ,36,38,39 have assumed theexistence of a constant relaxation time T. Thisassumption is often qualified by noting that T maydepend on K, the electron wave vector. However,Friedman40 has pointed out that it is likely thatunder some circumstances, the relaxation timeassumption may be entirely unjustified, and that,due to the narrow bandwidths, the scatteringmay not be amenable to a standard, one-phonondeformation potential treatment.

There are two important respects in which thenarrow bandwidths must be taken into account.The first relates to the validity of the band picture.With the mobility IJ- given byu

IJ- = (k~)< TV2>

~(:~) ~:::where v is the average thermal velocity of theelectron; W. the bandwidth; and a, the latticeconstant, the energy definition of the band statesrequires that

Thus, a lower limit on the mobility is given by

7

J. SCIENT. IND. RES., VOL. 28, JANUARY 1969

With a = 3X10-8 em, one finds that42•

> 0.1 W cm2

fL - kT V-sec

Hence, mobilities of the order of unity are on theborder-line of a band description. Mobilities of theorder of 0·1-1,0 are observed experimentally31,U and,therefore, their description by means of band motionis not in clear violation of the uncertainty relation.

But, since the bands are quite narrow in theabsence of lattice vibrational effects of a self-trappingnature, one must consider that the standard formulaeregarding phonon scattering may not be applicable.Rather one may be forced to use higher orders ofperturbation theory41, or even a change in basis fromthe Bloch representation to a localized representationmay be required28. Friedman40 estimated that theself-trapping effects of intramolecular vibrationswould not be important in the aromatic solids ofnaphthalene-anthracene type, and went on to deriveimproved formulae for various transport phenomenain the narrow band limit. His estimates have sincebeen not accepted and now it appears that self­trapping effects may actually be quite importantu .

Hopping Model

A second line of attack on the conduction problempictures the electrons and holes as jumping fromone site to another. As Eley first suggested, thiscould occur by tunnelling through the intermolecularbarrier rather than by phonon-assisted hoppingover the barrier1o,45,46. The tunnelling mechanismdoes not require that a charge carrier be raised agiven amount above the ground stale; therefore,the model cannot be rejected on the ba<;is of theexperimental temperature dependence of mebility.More generally, tunnelling probabilities will dependupon the vibrational quantum number and one mightstill expect to see a thermal activation effect. Inaddition, the population.of acoustic phonons willnot change much except at very low temperature(because of their low energy). Finally, the increasein the equilibrium thickness of the intermolecularpotential (ie crystal expansion) with increasingtemperature will tend to decrease mobilities withincreasing temperature, an effect opposite to thatproduced by thermal vibrations in a crystal ofconstant volume. Apart from the opaque questionof temperature dependence, quantitative calculationhas shown that simplified hopping models canaccount reasonably well for electron mobilities inanthraceneu ,48. But the state of the theory under­lying a hopping model is still in a rather weakposition. In this case, the lacuna is not that thebands are too narrow, but rather that they maynot be narrow enough, and further, one does notknow how to adequately treat the time-dependentproblem to get quantitatively accurate expressionsfor the ump probabilities.

"It is instructive to compare this condition with thatapplicable to the conventional wide band case. In thiscase with I" = eTlm", the requirement that (TIlT) <kT leadsto the condition that '1"> (mlm") x20 cm'/V-sec at roomtemperature [Eq (3) of ref 41; also ref 42]. While it ispossible that m" >m so as to allow mobilities of the orderof unity, I" # eTlm" for the narrow band case, as discussedin the text.

8

Recently, Glaeser and Berry&9 have made anattempt to decide which of the two extreme modelsis the more useful as a first approximation tounderstand the conduction mechanism in organicmolecular crystals. Anthracene was the principalsolid examined, but similar calculations have alsobeen given for naphthalene. A critical re-evaluationis made of the transfer integrals which have beencalculated from molecular orbital wave functions,particular attention being given to include the effectssuch as electronic pOlarization, whose importance wasnot estimated earlier. These transfer integrals havebeen used to examine the conduction problem in thetwo extreme limits: (i) in terms of simple bandtheory, in which a delocalized, tight-binding repre­sentation is used; and (ii) in terms of a simplehopping model where site-to-site hopping by reso­nance transfer (tunnelling through the intermolecularbarrier) is valid. Their calculations have shownthat the usual model of a band representation andweak phonon coupling is probably not the beststarting point for a discussion of charge mobility inorganic solids of the naphthalene-anthracene type.The bands are apparently too narrow for the simpleband model to hold; when the cfkcts of polarizationare included, the hands arc narrowed considerahlyand interaction with optical phonon would probablynarrow them further still. To take the narrownessof the bands into account and still retain thedelocali~ed picture is not a trivial problem28,fl.

On the other hand, ;l simple hopping model appearsto be indicated by theoretical considerations as­sociated with the small molecular interaction" (ienarrow bandwidth)28. The a",",umption that theresonance transfer is the time-limiting process leadsto quantitative predictions regarding the mobility ofexcess electrons or holes. .

It can, therefore, be concluded from the criticalre-evaluation of the two extreme models that thehopping model is superior to the band model, andthat the former gives a quantitative picture of thephysical mechanism underlying electrical conductionin organic molecular crystals of the naphthalene­anthracene type. However, it is recognized, aspointed by Glarum60, that the calculated transferintegrals and observed mobilities lie in a rangeintermediate between the domains of rigorous validityfor either model.

SummaryA comparative study is made of the applicability

of the two limiting models, band and hopping models,for obtaining a quantitative picture of the physicalmechanism underlying charge transfer in organicsemiconductors of molecular crystal type. In boththe models, the transfer integrals are calculated frommolecular orbital wave functions. But, most of theauthors have calculated these transfer integralswithout paying any attention to include, the effectssuch as electronic polarization. However, if theeffects of electronic polarization are consideredin the evaluation of the transfer integrals and themodified transfer integrals are used to examine theconduction problem in the two extreme limits:(i) in terms of simple band theory, in which adelocalized, tight-binding representation is used;

DATT: CONDUCTIO ' ~IECHANISM JN ORGA.NJC SEMICONDUCTORS

and (ii) in terms of a simple hopping modd wheresite-to-site hopping by re"onance transfer is valid,then the hopping model is found to be superiorto the band model, and gives a quantitative pictureof the phy"ical mechani"m underlying electricalconduction in organic molecular crystals of thenaphtha]cne-anthracene type. However, it should bepointed out that the calculated transfer integralsand observed mobilities lie in a range intermediatebetween the domains of rigorous validity for eithermodel.

AcknowledgementThe author is thankful to Prof B. D. Nag

Chaudhuri, Member, Planning Commission, Govern­ment of India, New Delhi, for many valuable dis­cussions and critically reviewing the manuscript.

References1. G.\RETT, C. G. n., Organic semirolldudors in Semi­

conduc/ors, edited by:-.J. B. Hannay (Reinhold PublishingCorp, "ew York), 1959, 634.

2. KEPLER, R. G., BI ERST EDT, P. E. & :YIERHIFIELD, R E.,Phrs. liev. Lett., 5 (1960), 503.

3. IXOKUCHI, H. & AKAMATU, H., cited in Solid slale physics,Vol 12, edited by F. Seitz & D. Turnbull (AcademicPress Inc, New York), 1961. 93.

4. Organic semicolld1tctors, Proceedings of an inter-industrycOllfermce, Chicago, 1961, edited by ]. ]. Brophy &]. W. Buttrey (The Macmillan Co, New York), 1962.

S. UKAMOTO, Y. & l-\RE:-:~En. \V., OrKanic semiconductors(Reinhold l'uhlbhin~ Corp, New York), 1964.

6. KO!\.DIANDEUR. J" COllductiuity in Physics and clwmistryof the organic solid statc, Vol II, edited uy D. Fox.:\1. M. Labcs & A. \Vcissucrgcr (Intcrscicncc PublishersInc, New York), 1965, 1.

7. MEIER, H., Angew. Che",. intPrnat. Edit., 4 (1965), 619.8. WEISS, D. E. & DaLTO, B. A., Cond'/lCtillg polymers in

Physics and chemistry of lilt' orga71ic solid state, Vol II,edited by D. Fox, M. M. Labes & A. Weissberger(Interscience Publishe," Jnc, New York), 1965, 67.

9. GUTMANN, F. & LYONS, L. E., Orgallic semicollductors(John Wiley & Sons Inc, New York), 1967.

10. DATT, S. C., VERMA, ]. J<. D. & AG, B. D., J. scient.indo lies., 26 (1967), 57.

11. IJATT, S. c., Growth of singte crystal.< of naphthalene andstltdy of somc eleclrical properties of naphthalene, Ph.D.thesis, University of Jabalpur, ] abalpur, 1968.

12. PICK, H. & WISSMAN, G., Z. Phys., 138 (1954), 436.13. METTE, H. & PICK, H., Z. Phys., 134 (1953), 566.14. NORTHROP, D. C. & SIMPSON, 0., Proe. II. Soc., A234

(1956), 124.15. GRAVATT, C. C. & GROSS, P. M., J. chern. Phys., 46 (1967),

413.16. RIEHL, N., Zh.fiz. KMm., 6 (1955), 959.

17. RIEHL, :\., Am,ln Phys., \'1-20 (1957), 94.18. DEXTER, D. H. & SEITZ, F., Ph)'s. Ret'. , 86 (1952),

964.19. Fox, D., Electronic states of aromatic solids in Electrical

conductivity in organic solids, edited by H. l<allmann &:fl.!. Silycr ([nter:-iciencc Publishers Inc, New York).1961,239.

20. "AKADA, 1., ARIG,\, 1\. & IcH"llYA, A., J. phys. Soc.Japan, 19 (1964), 1587.

21. MOTT, N. F. & GUR><EY, R. W., Eleclronic processes inionic cryslals (Oxford Uni\'ersily Press, London), 1948.

22. JOFFE, A. F., Sot'iet Phys. Solid St., 1 (1959), 1.23. JOFFE, A. F. & REGEL, A. R., Progress in semiconductors.

\'014 (Heywood & Co Ltd, London), 1960,237.24. MOTT, N. F., Proc. R. Soc., A146 (1936), 465.25. HARAS"'A, A., Proe. phys. malh. Soc. Japan, III-21

(1939), 679.26. GUBANOV, A. I., J. thea. Phys. USSII, 26 (1954), 139;

28 (1955), 401; 30 (1956), 862.27. GvBA:<OV, A. I., Zh. tekh. Fiz., 27 (1957), 2510.28. HOLSTEIN, T., Ann. Phys. (N. Y.), 8 (1959), 343.29. ~IORI:<, F. ]., Phys. J/Ev., 93 (1954), 1/99.30. HEIKES, R R. & ]OHNSTO>l, W. D., J. chem. Ph"s., 26

(1957), 582.31. KEPLER, H.. G., Phys. Rev., 119 (1960), 1226.32. LEBLA"C, O. H., J. chem. Ph"s., 33 (1960), 626.33. HEIUIEIER, G., WARFIELD, G. & HARRISON, S., Phys.

lIev. Lett., 8 (1962), 8.34. LEBLA>lC, O. H., J. chem. Phys., 35 (1961), 1275.35. THAXTON, G. D., ]ARNAGIN, R. C. & SILVER, 1'1., J. phys.

Chc", .. Jlhaea, 66 (1962), 2461.36. J(ATZ, ]. L., RICE, S. A.. CHOI, S. 1. & ]ORTNER, ].,

J. cllem. Ph)'.'., 39 (1963), 1683.37. MURELL, ]. N., Malec. Phys., 4 (1961), 205.38. S,LBY, R, ]ORTNER, ]., RICE, S. A. & VALA, 1\1. T.,

J. ehem. Phy'" 42 (1965), 733.39. RICE, S. A. & ]ORTNER, ]., Possible uses of high pressure

techniques jor the study of electronic states of nlolau/orcrystals, paper presented to the International Conferenceon Physics - Solids under High Pressure, Universityof Arizona, April 1965.

40. FRIED'IAN, L., Phys. 1Iet'., 133 (1964), AI668.41. FROHLICH, H. & SEWELL, G. L., Proc. phys. Soc, Land.,

74 (1959), 543.42. HERRING, C., Proccedi11gs of the i1~ternati011Ql conference

011 scmicondnctor physics, Prague, 1960 (Czechoslo­vakian Academy of Science, Prague), 1961, 60.

43. SILVER, M., RHO, ]. R, OLNESS, D. & ]ARNAGIN, R. C.,J. chem. Phys., 38 (1963), 3030.

44. SIEBRAND, W .. J. ehem. Phys., 41 (1964), 3574.45. ELEY, D. D., 1NOKUCHI, H. & WILLIS, M. R, Discus.

Faraday Soc., 28 (1959). 54.46. ELEY, D. D. & PARFITT, G. D., Trans. Faraday Soc., 51

(1964), 1529.47. KEARNS, D., J. ehem, Phys .. 35 (/961), 2269.48. KnLER, R. A. & RAST, H. E., ]. chern. Phys., 36 (1962),

2640.49. GLAESER, R. M. & BERRY, R. S.,]. chem.Phys., 44 (1966),

3797.50. GURUM, S. H., Physics Ghe",. Solids, 24 (1963), 1577.

9

Determination of Force Constants*V. P. S. NAIN

Physics Department, Rajasthan University. }aipur

&

M. L. SHARMAAgrawal College, }aipur

For such potentials the second and third virialcoefficients, the isothermal Joule-Thomson coefficient,coefficients of viscosity, thermal conductivity anddiffusion can be given by the equations of the type

are determined for various values of T* aroundthe expected value. If log R is plotted againstlog (./11), two curves will be obtained for the twotemperatures. The intersection point will givethe values of Rand ./11 satisfying the experimentaldata at the given temperatures. If the processis repeated for different pairs of temperatures, themean of all the intersections will give the best fitvalues of a and ./k. This method thus requiresaccurate data at few temperatures only to givereliable values. Another simplified way to usethis method is to tabulate experimental values oftjJ(T*) = ~/R for a series of arhitrarily chosen valuesof a for the two temperatures. A comparison ofthese experimental values of <jJ(T*) with the theoreti­cal values will give the value of T* and hence

where ~ is the concerned coefficient; R, a constantwhich depends on a or r",; and q,(T*), some functionwhich depends only on T*.

Translational MethodIn the translational method, also named aft'~r

Lennard-Jones· who first employed it, log of theexperimental values of ~ is plotted againstlog T on a transparent graph paper. Another plot oflog q,(T*) against log T* is drawn on the same scaleas for the previous plot. The former plot is thensuperposed on the latter by simple translationsparallel to the two axes. The translation alongthe log tjJ(T*) axis gives log R and hence the valueof a, while translation along the log T* axis giveslog (./k). This method requires data over a largetemperature range and unless there are some dis­tinguishable peculiarities in the curve it is notpossible to successfully exploit the method. Themethod thus is not always very reliable thoughit is a quick one and permits easy comparison ofseveral potentials if the theoretical curves are plot­ted on the same graph paper.

Intersection MethodThe intersection method of Buckingham7 requires

experimental data only at two temperatures at whichthe quantities

log R = log ~-log tjJ(T*) ... (3)

and

THE main techniques which have been used forthe determination of intermolecular forces arebased on (I) quantum mechanical calculations,

(2) spectroscopic observations, (3) relaxation methods,(4) beam scattering, and (5) macroscopic properties.

The discussion in the present review will beconfined to the determination of force constantsthrough the macroscopic properties of gases. Thedependence of such properties of gases on the forcelaws provides a convenient means of obtaining reli­able information about these forces. The physicalproperties thus used are: (I) equilibrium, (2) trans­port, and (3) crystal properties. Out of these theequilibrium properties find a definite preferenceover the others due to the existence of accurateand well-understood theories correlating the forceconstants and the macroscopic properties. Thetransport properties, on the other hand, are less suitedto an investigation of intermolecular forces becauseof the presence of internal degrees of freedom. Thetheory of crystal properties involves certain assump­tions like pair-wise additivity, etc, which may notbe strictly valid.

The various intermolecular forces are describedin terms of different potential functions which havebeen suggested on semi-empirical basis. All sortsof omission and commission made in the choice ofa potential model have to be absorbed into the nu­merical values of the adjustable potential parameterswhose values are obtained by the best fit of theexperimental data on some appropriate macro­scopic property. The criticality of the method infitting considerably affects the reliability of theforce constants thus determined. These methodsof determining the potential parameters from theexperimental data on bulk properties of gases havebeen discussed by Strehlowl , Whalley and Schnei­der2, Srivastava and Srivastava3, Saxena4, Sri­vastava and Madan5, Mason and Monchick (privatecommunication) and others. The methods whichhave been often used for the determination ofpotential parameters from the experimental dataon bulk properties are: (I) translational method,(2) intersection method, (3) ratio method, and(4) least squares method.

The above methods are reviewed and comparedwith the other methods (suggested by the presentauthors) in this paper.

The central potentials can be represented in theform"'(r) = .f(a/r) ... (1)

• Paper presented at the convention organized by thePhysical Research Committee of the Council of Scientific &Industrial Research at the Andhra University, Waltair, inFebruary 1968.

10

~ = Rq,(T*)

log (./k) = log T -log T*

...(2)

... (4)

... (9)

where bo = i7tN(J3, B*(1'*) is a function of reducedtemperature 1'* and N the Avogadro number. Thevalues. of the function B*(T*) for the L-J(12-6)potential have been given by Hirschfelder et al8•

The isothermal zero pressure Joule-Thomson co­e!ficlent, 4>0(1'), for such a potential function isgIven by

rpo(T) = bo[Bi(1'*)-B*(1'*)] ... (8)

where Bi(1'*) = 1'*(dB*ld1'*). The values of Bi(1'*)also are given by Hirschfelder et al8•

From Eqs (7) and (8) we get

4>V) [B;(T*) ]B(1') = B*(T*) -1 =.F*(1'*)

The right-hand side, F*(1'*), of Eq (9) is a functionof 1'* only: while the left-hand side involves simplythe expenmentally determined quantities. Thusknowing the experimental values of 4>0(1') and B(1')at a common temperature l' the values of F*(1'*),1'*. and hence Elk can be determined directly.ThIS :-alue of Elk in conjunction with Eq (7) or (8)WIll yIeld the value of (J. These values of the forceconstants (Elk and (1) will correspond to the parti­cular temperature l' at which the experimentaldata are used.

The. average. values of Elk and (J for L-J(12-6)potentIal for mtrogen as determined by Saksenaet alII at various temperatures are 95·3°K and 3·66 Are.spectively. These values are in good agreementWIth those determined by using the experimentaldata on second virial coefficient only and reportedby Hirschfelder et al8•

The importance of the above method lies in thesimultaneous use of the two equilibrium propertieswhIch de!>Cnd upon the intermolecular potentialfunctIon dIfferently. There is now enough evidence(~ason, E. A: & Monchick, L., private communica­tion) to belIeve that the second virial coeffi­~ient is de~endent on the area of the potential wellInstead of ItS form. Thus, various potential func­tions having different shapes but the same areaof the potential well will successfully predict thismacroscopic property. This leads to the conclu­sion that the use of only the second virial coeffi­cient experimental data may yield the force cons­tants which are not the true representatives ofthe actual potential function. The Joule-Thomsoncoefficient i~ this respect is a better property forthe evaluation of these parameters. Besides, theuse of a single physical property, as is done in theearlier methods2, results in giving average valuesof these parameters over a certain temperaturerange. These average values though capable ofreproducing the experimental data do not revealthe temperature dependence of these parametersif it exists. Such temperature dependence ha~been observed in some casesl2 and the most notableof these is the the case of carbon dioxidel3. Oneof the possible reaso~s7 might be the unsuitabilityof the used potentIal function to describe thisproperty.

In an attempt to ascertain this temperaturedependence Saksena et alII have determined poten­tial parameters for CO2 as a function of temperature.

... (5)

NAIN & SHARMA: DETERMINATION OF FORCE CONSTANTS

Elk for each value of a. Thus, if the two sets ofcoupled values of Elk and a are plotted, their inter­section point will give the unique values of Elk and a.

Ratio Method. The ratio method given by Hirschfelder et al8

IS based on the fact that the ratio of the two valuesof ~ wi!1 depend only on 1'* and will be equal tothe ratIO of the two corresponding <J!(1'*) values.Thus, if we write

y = <J!(1'2*)/<J!(1',*) ... (6)

the.n by trial and error a value of Elk can be foundwhIch wdl make X = Y for different pairs of tem­peratures. As it is often difficult to try all thevalues of Elk, an approximate value determinedeither by the first method or by some empiricalrelatIOn between Elk (ref 8 a.nd 9) and such physicalquantIties as cntlcal and bOlhng points is taken.

A convenient modification of this method hasbeen used by Srivastava and coworkers3,5 and bySaxena' successfully for the determination of para­meters from transport properties. This modifiedmethod may be termed as the graphical ratio me­thod. In this the experimental values of X (= ~2/~1)

are plotted agaInst 1'1 or ~I and similarly the valuesof Y [~<J!(T2)/<jJ(1';)] are plotted against 1'j or <J!(1'j).For vanous values of X = Y corresponding valuesof 1'1 and 1'; can be obtained from the two plotsrespectIvely. The ratio of 1'j to 1', will thencegIVe the value of Elk, which in conjunction withEq (2) will give the value of a. For most of thecases the graphical ratio method is found adequate,as due account can be given to the errors in thedata and of the systematic trends and peculiaritiesover an extended range by careful translations.

Least Squares Method

In the least squares method as described byDemig'O approximate values of Elk and a are chosen.T~ereafter, using the least square criterion andmlmmlZIng the deviation between experimentaland calculated ~ values the corrections to Elk and(J are determined. If the corrections are more thana few per cent the process is repeated again usingbetter approximations. This method, thoughcapable of yIeldIng reliable values, is difficult fromthe computational point of view and is, therefore,not commonly employed.

The properti~s more commonly employed forthe deter~lnatIOn .of potential parameters aresecond vlTlal coeffiCients and viscosity. Of thesethe use of second vi rial coefficients and their tem­perature dependence has been advantageouslyreplaced by second virial and Joule-Thomson co­effiCIents at a common temperature by Saksena etall.'. In wha~ follows below we describe this aspectb.nefly and dISCUSS critically exploiting the calcula­tions done on this method for the gases NandC.02• For central potentials the second virial ~oeffi­clent, B(1'), is given by

B(1') = boB*(1'*) ... (7)

11

J. SCIENT. IND. RES., VOL. 28, JANUARY 1969

Their calculated values of Elk and cr show a de­finite and significant dependence on temperature.However, scarcity of reliable data on Joule-Thomsoncoefficient over a wide temperature range for CO2

makes it difficult to explain this variation withcertainty and in all probability the simple L-J(12-6)potential is not adequate for this complicatedmolecule

In the light of the above discussion this methodfinds preference over others wherever reliable ex­perimental data on the two equilibrium properties,viz second virial coefficient and Joule-Thomsoncoefficients, are available.

All the above methods, except the preceding one,employ a single bulk property for the determinationof the force constants. The constants thus deter­mined from one property vary markedly from theconstants determined with the help of another pro­perty. Consequently, it has become desirable thatthe parameters obtained from one transport pro­perty, preferably viscosity, should be used tointerpret the data on transport properties only;similarly the parameters from an equilibrium pro­perty should be used for calculations of equationof state and thermodynamic propertiesS. Thissuggests that these force constants are not the truerepresentatives of the molecular interactions whichare common to all these physical phenomena. Toovercome this it is preferable to use simultaneouslytwo macroscopic properties belonging to di fferentclasses (transport, equilibrium or crystal properties)to evaluate the force constants. With this viewNain et al'4 have suggested a methocl which utilizesthe experimental second virial coefficient and visco­sity data simultaneously. They have tested theappropriateness of the method on the L-J(12-6)potential function by calculating second virial andviscosity coefficients for Kr.

The second virial coefficient, B(T), for the centralL-J(12-6) potential is given byB(T) = 5·rrNcr3B*(T*) ... (10)

The different symbols bear the usual explanation.The coefficient of viscosity, 1), for pure gases is

given by(MT) 112

1) X 10' = 266·93 crTQ I2,"i'(i'*) ... (11)

where M is the molecular weight and Q I2,2J'(T*)the reduced collision integral. The values of QI2,2)'(T*)for the (12-6) potential are given by Hirschfelderet also

With the help of Eqs (10) and (11) the finalexpression can be written as

[B(T)]2[1)]3 [B*(T*)]2(MT)3t2 = 3·0367 x 10-14

[hl"~"I;(T*IT3 == Q*(T*)

... (12)

The right-hand side of Eq (12) is a function of1'* only, while the left-hand side involves simplythe experimentally determined quantities. Thus,the knowledge of B(T) and .~ at a common tem­perature T and the molecular weight M gives thevalue of left-hand side in Eq (12), which when com­pared with the theoretical values of Q*(T*) willyield the value of 1'* and hence Elk. This value

12

of Elk in conjunction with Eq (10) or (II) willenable the determination of the value of cr. Theseparameters thus determined will correspond tothe particular temperature l' at which the experi­mental data were used.

The success of the method and the parametersthus determined was tested by calculating theviscosity and the second virial coefficients usingthe same parameters. From these calculationson Kr, CO. and CH4, Nain et all' concluded thefollowing:

(1) The set of parameters determined from com­bined viscosity and virial data are capable ofinterpreting both the viscosity and second virialcoefficients with desirable accuracy.

(2) The force constants determined from pureviscosity data are unsuitable in predicting the secondvirial coefficients and vice versa.

(3) In certain cases (Kr) the combined fit repro­duces B(T) and 1) better than the 'best tit' forB(T) and .~ separately. This deviation may bedue to either poor curve titting in the determinationof the force constants from B(T) and .~ individuallyor the use of a smaller temperature range as com­pared to that employed in the present investigation.

(4) The values of Elk determined at different tem­peratures varied insignificantly for Kr and CH•.while for CO2 the variation was as much as ± 5%from the mean value without any systematic trencl.Thus the temperature dependence of the parametersfor CO" discussed earlier could not be confirmedhere. -

(5) The method lays more emphasis on theviscClsi ty data as compared to the second virialcoefficients. This, therefore, will result in moresatisfactory prediction of the viscosity than thesecond virials.

Summary

Various methods used very often for the deter­mination of potential parameters from the macro­scopic properties of gases are briefly reviewed. Twoadditional methods, one involving the two efjuili­brium properties, viz second virial and Joule-Thomsoncoefficients, and the other involving the equilibriumand transport properties, vi?' second virial andviscosity, simultaneously suggested recently arediscussed at length. Calculations performed onseveral gases including monatomic through com­plicated molecules are discussed.

Acknowledgement

The authors arc thankful to Dr M. P. Sakscnafor his helpful discussions and criticism. One ofthem (V.P.S.N.J is thankful to the Council of Scientific& Industrial Research, New Delhi, for linancialassistance.

References

1. STREHLOW. R. ,\., .r "hl'ln. Pln-s .. 21 (1953), 2101.2. \VI-I:\LLEY, E. & SCI-I~EIDI·;J{, \V. (;.,,/. r.!l.r:m. Phys., 23

(1955). 1644.3. SRIV~\STAV:\, B. ~. 8:: SI{[V;\ST;\V:\, K. I'., Plt)'sira, 'sGrav .•

23 (1957). 103.4. S,\XENA. S. C.. Indian.f. PhV8 .. 29 (1955). 453. 587.5. SRIVASTAVA, B. N. & l\L\DA:'>l, M. P., 1'roc. ph)'s. Soc.,

A66 (1953), 277.

LOEHMAN et at: ARC TECHNIQUES IN THE PREPARATION OF INORGANIC MATERIALS

6. LE"NARD-JO"ES, J. E., PYoc. R. Soc., AI06 (1924), 463.7. BUCKINGHAM, R. A.. Pyoc. R. Soc., A168 (1938), 264.8. HIRSCH FELDER, J. 0., CURTISS, C. F. & BIRD, R. B.,

MTGL (John Wiley & Sons Inc, New York), 1964.9. SAKSENA, M. P. & SAXENA, S. C., Indian ]. puye appl.

Phys., 4 (1966), 86.10. DE>lIG, W. E .. Statistical adjustment of a data (John

Wiley & Sons Inc, New York), 1943.

11. SAKSENA, M. P., GANDHI, J. M. & NAIN, V. P. S., Ghem.phys. Lett., 1 (1967),424.

12. SAKSENA, M. P., NAIN, V. P. S. & SAXENA, S. C., Indian]. Phys., 41 (1967),123.

13. MACCORMACK, K. E. & SCHNEIDER, W. G., J. chem.Phys., 19 (1951), 849.

14. NAIN, V, P. S., SAKSENA, M. P. & SHARMA, M. L.,]. phys. Soc. Japan, 26 (1969), (in press).

Arc Techniques in the Preparation of Inorganic Materials

R. E. LOEHMAN, C. N. R. RAO', J. M. HONIG & C. E. SMITH

Department of Chemistry, Purdue University, Lafayette, Indiana 47907, USA

T HE arc technique was first used by Hare1

in the synthesis of inorganic materialslike CaC., C;t and P. Later, Moissan' de­

veloped the technique of using carbon electrodes inair or carbon monoxide atmosphere to attain tem­peratures of up to 4000°C, a technique still beingwidely used, Krol13 has described an arc meltingfurnace for processing refractory materials in inertatmospheres, employing tungsten electrodes anda water-cooled hearth. Apart from these isolatedexamples, electric arcs seem to have been little usedin inorganic preparative chemistry. Recently,interest in this technique has been revived, asexemplified by some recent publicationst-6. Usinga single arc, Reed4 has melted a wide variety ofmaterials including metals, alloys and compoundssuch as ThO., BeD, CeO., Al.o3, ZrO., etc. Itwas felt that the attention of a wider groupof scientists needs to be drawn to the simplicityof the technique, and its great utility in carryingout a large number of high temperature chemicalreactions. The present paper reviews the design andtechniques followed in the construction and opera­tion of the arc furnace. The observations re­ported are based largely on experiences gained atthe authors' laboratory with equipment adaptedfrom the design by Reed4 and Reed and Pollard'.

Single Arc

Basically, an arc is generated by the passage ofcurrent from a small thoriated tungsten cathodeto a crucible containing the materials to be reacted,acting as an anode (Figs. 1 and 2). The temperatureof the plasma exceeds a minimum of 100000K re­quired to maintain sufficient ionization and con­duction, and an upper limit near 300000K, set bythe energy density that can be maintained. Theshape of the cathode tip is particularly importantin the melting of non-conductors, since the highvelocity magnetohydrodynamic flame which issuesfrom the tip is a result of the high current densitythere. Therefore, the tip should be ground to a

• Visiting Professor of Chemistry, Purdue University,1967-68. Permanent address: Department of Chemistry,Indian fnstitute of Technology, ]{anpur.

point with an included angle in the range30-60°.

Power is conveniently supplied by rectified powersets used in standard welding operations, thoughmotor generator sets or batteries with series resis­tance ballast are satisfactory in many instances.

. Typical operating conditions involve currents ofthe order of 70 amp at 15 V passing through a gas.These gases circulate in a chamber enclosed at thebottom by the cold hearth, at the top by an alu­minium frame holding the cathode, and surroundedon the sides by a cylindrical pyrex or vycor glasssleeve.

Arcs may be maintained in inert or reducingatmospheres such as argon, helium, nitrogen orhydrogen in the range 100-760 torr. Traces ofoxygen or volatilized carbon attack the tungstenelectrode. Thus, it is important to getter the gasesby passage over heated active metals (Ti at 500°C).If it is desired to operate in oxygen, a carbon elec­trode must be used, but it will produce carbonmonoxide by oxidation of the cathode and thusaffect the oxygen partial pressure in the system.

The crucible, hollowed out from a cylindricalcopper hearth, is maintained near room temperatureby water flow through cooling channels. An arcis first struck by lowering and swivelling the elec­trode so that it touches a spot on the cold hearth.The current is raised slowly while the cathode issimultaneously withdrawn, so as to maintain thearc, which is then moved until it bathes thematerials to be reacted in the crucible. The currentis increased until the material has reacted in themolten state; on turning off the current, one gene­rally obtains a frozen button.

With a water-cooled hearth, enormous tempera­ture gradients develop at the interface betweenthe melt and the crucible. In all probability, avery thin skin of the sample separates the melt fromthe copper hearth; in this sense the sample formsits own crucible, and serious contamination withcopper is avoided. The method thus lends itself tothe synthesis of material in highly purified form.

Details concerning the construction of the cathodeare shown in Fig. 1. The principal problems are

13

~ Water Inlet Gnd Oullt l

J. SCIENT. IND. RES., VOL. 28. JANUARY 1969

(a) to insulate the cathode from the remainder ofthe system at ground potential by means of a ceramicsleeve, and (b) to keep the cathode tip reasonablycool, by directing a flow of cool gas over it via nozzlesin the tip. Gas circulation through the chamberis achieved through these openings. as well asthrough holes in the hearth itself; the location ofthe ports is indicated in Fig. 2. For more efficientcooling to reduce the possibility of contaminationof the sample by tungsten vaporized from thecathode, we have constructed a water-cooled cathodewhich has a replaceable thoriated tungsten tip(Fig. 3). Swivelling action is achieved by insertingthe electrode in a steel ball which is aIlowedto rotate on a support in the top part of the frameresting on the hearth. Although we have not doneso in this laboratory, flexible brass or stainless steelbeIlows could be substituted for the steel ballbearing to connect the cathode to the furnacechamber and allow the necessary freedom of move­ment for the cathode. It is necessary to shieldoperating personnel from the intense UV radiationgenerated by the arc.

We have found the arc technique to be ofparticular value for the preparation of metal oxideswith varying degrees of stoichiometry. Thus, wehave prepared the oxides TiO. (O<x<2), VO.(O<x<2·S), NbO. (O<x<2·S) and mixtures of theseby using stoichiometric quantities of the metaland its corresponding oxide in the highest valencystate. Other compounds made in this laboratory

seollifltf'\. Ii:> ,; 20......":\..

....p~t

II , I\' :,':~ -.

i, ,I I 0·....

I I II I II I II I I

I, ,

II

II II,

II

Fig. 1 - Side view of single arc melter drawn approximatelyto scale [Crucible is in the central, hollowed-out section of thewater-cooled hearth; the cathode is fitted through a sphericalholder that can swivel in the aluminium frame forming thetop. A pyrex or vycor sleeve separates the top and bottom]

to em.

5cm.

anneetor for Power Cob'e

flIII III

' 1 1111

' 1 "11I II I

1111 1,11111 I11 ,'111I 1II1 T.tlon Sl••••

11 11 1,I1II'!I'III II I~ Retolnlng Ringo

1 11 1I II I ("""Hoot Shiel~

.111/

I " I I \-.. R.tolnlng Ring,I 'I111 1I II I --Copp.,\11/"lJ,', .

Copper Base of Arc Furnace _Thorloted Tun9Stefl TIp

Fig. 2 - Top view of single arc hearth [Outermost ringrepresents feed line for circulation of inert gases through the

hearth into the reaction chamber]Fig. 3 - Water-cooled cathode [Section through centre.

approximately to scale]

14

LOEHMAN et al: ARC TECHNIQUES IN THE PREPARATION OF INORGANI!: MATERIALS

Ill', .

--...--d

Argon Inlet

a

some practice, but the colour of the molten samplecan serve to help in determininl" when the propertemperature is attained. The pulling rod is thencranked down until the tip just touches the melt.The melt usually wets the rod at this point andthe slow pulling process can be started. If theplasma arc is properly adjusted, an irregular cylinderof solid sample (most likely polycrystalline) willemerge from the melt. By controlling the rate ofpull and crank rotation. the sample can be neckeddown until only one single crystal remains; thisalso requires practice. This is equivalent to themethod of starting the pulling of a single crystalusing a single crystal seed on the end of the pullingrod. Once the sample has been necked down, slow,careful turning of the crank should produce asingle crystal boule whose diameter is determinedby the rate of pull and the placement of the torches.The screw drive must be turned periodically tomaintain the level of the melt. Nice single crys­tal boules of Ti30 6• NbO and Ti,03 have been grownin this laboratory using the techniques described

W::Jter Outlet

Fig. 4 - Side view of tri arc crystal pulling furnace approxi­mately to scale [a, water-cooled pulling rod; b, crucible ofhigh density graphite; c, handle; d, crank; e, rotatmg seal;

and f, screw drive]

include Ln,03' LnCr03, LnMn03• LnFe03 (Ln =rare earth) and CeO,-Y,°3 and TiO,-Y,°3 mixtures.The buttons obtained from arc melting are oftenquite satisfactory for many electrical and othermeasurements. The method also has been foundto be very convenient for carrying out inorganicsyntheses requiring high t~,?,peratuer.s. Forexample. when equimolar quantities of TIO andVO are melted together the resulting bead showsa phase separation into a dark .outer :egion of ~he

composition (V.Th-.1.03and a Silvery Inner por.tlOn(V.TiyO,). This illustrates that the arc techniquecan be quite useful in the study of high temperaturephase equilibria.

Tri ArcReedl has pointed out that if a material is suit­

able for growing single crystals from the melt,buttons of the material will cool with the formationof large crystal grains. One can construct a fur­nace suitable for pulling single crystals of thesematerials by slightly modifying the single arc fur­nace described previously. The side view of thetri arc furnace is shown in Fig. 4. The main dif­ferences between the single and tri arc furnacesinvolve the substitution of a water-cooled pullingrod (a) in the position occupied in the single arcmelter by the cathode. a crucible (b) of high densitygraphite which can be raised and lowered and theuse of three symmetrically arranged thoriated tungs­ten cathodes (torches) instead of one. The pullingrod can be raised and lowered by turning the handle(c) which is connected to the pulling rod througha rack and pinion gear drive mechanism. Turningthe attached crank (d) allows the pulling rod tobe rotated on its axis. The lower part of the pul­ling rod consists of two coaxial tubes, with a waterinlet to the annular region. and an outlet from thecentral tube through a rotating seal (e). The bot­tom of this assembly is threaded to accept a shortreplaceable tungsten rod, the only part of thepulling assembly which ever touches the moltensample. A water flow rate sufficient to keep thetungsten pulling rod cool, thereby minimizing tungs­ten contamination, is maintained during the courseof pulling a crystal. A gas-tight .seal ~hro?gh thealuminium top of the arc furnace IS mamtalned bythe tight fit of the pulling rod in ~ teflon bushing.In series with each of the torches IS a water-cooledballast resistor (R~O·5 ohm) which serves to allowthe striking of the arc from the second and thirdtorches once the first has been struck and also tostabilize the plasma arc once all three torches are on.

The crucible consists of a high density graphitecylinder with a slight concavity machined on thetop. The cylinder fits tightly in a hole boredthrough the copper base of the arc furnace but canbe moved upward using the screw drive (f) at thebottom of the furnace. This allows the level ofthe melt to be maintained as material is withdrawnin the form of a solid single crystal.

In practice the pulling of a single crystal is ac­complished by starting all three torches andadjusting the current and the placement of thetorches so that the top surface of the sampleis slightly above its melting point. This requires

15

J. SCIENT. IND. RES., VOL. 28, JANUARY 1969

Fig. 5 - Single crystal boule of NbO still attached to thepolycrystalline bead from which it was pulled

here. In Fig. 5, a crystal boule of NbO obtainedby this technique is sljown as a typical example.

Conclusion

Modifications of the apparatus described herecan readily be made to allow the arc technique tobe applied to the melting of fine powders, zonerefining, arc casting, rapid quenching or for use asa plasma torch'.

It may be of interest to compare the arc to otherheat sources available for the preparation of in­organic materials. An electron beam could be more

16

intense than an arc, and the high vacuum in theformer case could be useful in removing gases fromthe solid samples. However, the inert atmospherein the arc is helpful in minimizing evaporation ofcomponents. The arc technique has the advantageover the induction furnace in that it is able to heatnon-conductors directly. The economy and con­venience of the arc furnace compared to othermethods should make it a valuable tool in anymaterials preparation laboratory.

Summary

Techniques for the ready preparation of inorganicmaterials for solid state research are discussed. Withthe single arc furnace, polycrystalline beads maybe made easily, while the tri arc furnace allows oneto pull single crystals of a variety of materials. Theproblem of reaction between sample and cruciblematerial is eliminated in both these methods.

Acknowledgement

The authors wish to acknowledge support forthis project from ARPA interdisciplinary researchgrant No. SD-102.

References1. DOREMUS, C. A., TYans. Am. electy. Soc., 13 (1908), 347.2. MOISSAN, H., LeFouy Electyique (G. Steinheil, Paris),

1897.3. KROLL, W., Trans. electyochem. Soc., 78 (1940), 35.4. REED, T. B., Mat. Res. Bull., 2 (1967), 349.5. REED, T. B. & POLLARD, E. R., ]. Cyystal CYowth, 2

(1968), 243.6. BARTLETT, R. W., HALDEN, F. A. & FOWLER, J. W., Rev.

scient. Instyum., 38 (1967), 1313.

The Applications of Radioisotopes in Metallurgy in India-PresentPosition & Future Potentialities

V. K. IYA

Isotope Division, Bhabha Atomic Research Centre, Bombay 74

To review fully the present status and futurepotentialities of the applications of radio­isotopes in metallurgy in India is by no means

an easy task. It was only in 1958 that a beginningwas made in the production of radioisotopes inthis country, using the first reactor APSARA.The availability of the powerful CIRUS reactorin 1960 made it possible to produce most of thecommonly required radioisotopes in quantities andspecific activities adequate to meet the needs ofindustrial applications. Simultaneously, the develop­ment of nuclear electronic equipment at Trombaystimulated more and more institutions to workon the application of radioisotopes. A numberof training programmes in certain areas of indus­trial applications like radiography and activationanalysis, radiochemical techniques and handlingof isotopes have been organized at the BhabhaAtomic Research Centre (BARC). Besides this,actual assistance is being provided, wheneverrequested, in the planning and installation ofradioisotope laboratories.

RadiographyIndustrial isotope radiography has been the most

important industrial application in this countryand is in regular use today in more than 65 differentundertakings either for production control withinfactories or for inspection during the constructionof new installations. The users include all the majorfertilizer factories and oil refineries, several thermaland nuclear power stations, electrical and heavymachinery industries, and important defence in­dustries involving the production of aircraft, tanks,guns, ships, etc. More than 100 radiography cameras,most of them containing 5-20 C of 19211' and someup to 10 C of eoCo obtained from Trombay, are inregular use. The demand for cameras is expectedto rise steeply in the coming years, and the futuredevelopmental effort will be in the design of improvedmodels of lighter weight, of cameras taking highercuriage of eoCo and 192fr, and of new cameras takingisotopes like 17OTm. In its efforts to promote andactively encourage the spread of inspection usingisotopes, the Isotope Division also maintains asmall service group to carry out mainly non-routineand specialized radiography jobs and those requiringguaranteed quality. The Division also assists theIndian Standards Institution in evolving standardcodes of practice in radiography.

However, achieveQlents to date are modest com­pared to the achievements in other countries. Theeconomic benefits reported in some of the advancedcountries by the use of isotope radiography aretruly enormous. In UK, the figures for 1961indicate that about 700 radiography cameras werein use, effecting an estimated saving of about

$ 3 million. In USA, the savings in 1963 wereestimated at about S 7 million and in the USSR,where 3000-4000 cameras are in use, the savingsare estimated to be about S 22 million l . Directsavings result from lower capital cost for alternativeequipment for inspection; savings in scrap andincreased productivity; and savings in labour.Besides this, large intangible savings are effectedby increased safety and fewer complaints. Im­portant applications like welding control of steamboilers and pipelines and ship plates have helpedin decreasing hazards to life and property and haveshown the importance of isotope technology in amodern industrial society.

Tracer TechniquesRadioisotope tracer techniques have found a

wide variety of applications in metallurgical pro­cesses and research. The ease with which variousmaterials and phases can be labelled with radio­tracers, the extreme sensitivity with which theradiations can be measured, and the valuable know­ledge and benefits obtainable have made radio­isotopes an indispensable tool for such investigations.Notwithstanding all this, very few metallurgicalinstitutions and industries in this country makefrequent use of tracer techniques.

Apart from the BARC and the Indian Institute ofTechnology, Bombay, radioisotopes are employed astracers for metallurgical investigations only at theIndian Institute of Petroleum, Dehra Dun. Radio­isotope work in these institutions is mainly directedtowards diffusion and metal wear studies. In theindustrial field, it is only at Bhilai that tracer tech­niques are employed for studying the wear ofrefractory linings, the mixing of molten metal andin certain other processes. Tracer laboratories arein the process of being set up' at the NationalMetallurgical Laboratories and the Tata Iron &Steel Co in Jamshedpur and at the Indian Instituteof Science, Bangalore.

A few typical instances of how valuable resultscan be obtained by using radioisotopes as tracers canbe cited. By the addition of radioactive tracers to aproduct, it is possible to follow it through severalsteps in the production line and afterwards confirmits origin by a simple activity measurement. Thishas practical use in the identification of specialqualities. One interesting example is the tagging ofsteel carried out in Sweden. It was required thattwo steel works, which delivered tubes for heat ex­changers to a nuclear reactor, should certify thatevery tube at delivery had the approved composi­tion. Analysis of the highly alloyed steel was verytime consuming. It was, therefore, preferred toadd a small quantity «10 mC/ton) of a radio­isotope with medium life and suitable metallurgical

17

J. SCIENT. IND. RES., VOL. 28, JANUARY 1969

behaviour. 182Ta was chosen as tracer, the amountadded not affecting the quality of the steel. Later,one of the works received an order for tubes witha different composition, for which a similar identi­fication demand was prescribed. It was taggedwith 192Ir. The final products, tubes and tubingdetails were measured in the second case with ascintillation counter with variable discriminatorlevel. When this was set for measuring pulsescorresponding to Y-energies above 0·65 MeV, onlythe radiation from 182Ta was recorded. With thediscriminator set to accept Y-energies above 0·10MeV, both 192Ir and 182Ta tagged tubes showedactivity by which they could be distinguished fromuntagged material. The usefulness of the taggingmethod was clearly demonstrated for the identi­fication of two different qualities of steel2.

In other cases, tagging of steel baths has beenperformed, for instance, to avoid having experi­mental heats being treated and delivered as stan­dard qualities by mistake. For this purpose, variousshort-lived nuclides, such as uCu, 198Au or 187Whave been useds.

Metal Wear

Tracer techniques have been widely employedto study metal wear in order to improve the per­formance of engine parts in automobiles, tractors,ships and aircrafts. Owing to their very highsensitivity, radiotracers allow the detection ofextremely small values of wear and considerablyreduce the time of investigation. The conventionaltechnique involves irradiation of the engine partunder investigation in a reactor. This makes thewhole component radioactive and the activity isthen traced in the lubricant or metal powderproduced.

A recent development, the differential radioactivemethod, has increased the scope of the tracer tech­nique by obviating the high radioactivity of thecomponent which used to be a major drawbackof the technique. The method enables the studyof metal wear after reducing the radioactivity bya factor of 1000 or more, making it possible to carryout investigations without any radiation protec­tion. Components are irradiated in an acceleratorby a thin beam of charged particles, and a smallspot of relatively low radioactivity is activatedon the part to be tested. The part is then mounteddirectly on the running mechanism, and the radio­metric devices record the decrease in the activityof the surface layer caused by wear, depending onthe actual operating conditions. This novel tech­nique for continuous or periodic control of wearunder working conditions without stopping ordismantling the machine is now being widely usedin the engineering industry in USSRc.

Studies with tractor engines in relation to quan­tities and abrasive qualities of dust and the rateof wear on piston rings have shown that dust particlesof average diameter 0·1-0,2 I" caused the maximumwear. The life of CSEPEL engines of Budapestbuses has been doubled by the introduction offilters, chosen after investigations with radioactivetracers. Changes in the concentration and natureof dust in an engine could leadto variation between

18

1 and 10000 in its life. Wear was found to bepractically independent of the loading5.

Radiorelease TechniqueConsiderable improvements in labelling tech­

niques have taken place in recent years. Taggingof a variety of materials, without regard to theirchemical or physical form, may be accomplishedby incorporating 85Kr into the solid substance tobe labelled6. This is performed by bombardmentof the material with ionized krypton gas or bydiffusion of the gas under high temperature andpressure.

The versatility of 85Kr as a tracer lies in the factthat almost any material may be labelled withit. The degree to which absorption of the gas occursis a function of the physical structure of the solidmaterial. Thus while pyrolitic graphite has beenlabelled with 8sKr up to 1 C/g, for steel samples.the specific activities obtainable are far less, andcorrespond to only a few microcuries per gramas the absorption of gas here occurs only withina few microns of the surface. Any process,chemical or mechanical, which disturbs the sur­face, causes a proportional loss of krypton and,consequently, of its radioactivity. This techniqueof labelling has rendered possible applications likethe measurement of the erosion of turbine blades,the wear of bearings and the kinetic properties ofthe refractory metals at high temperatures'.

Non-active Tracer MethodBesides the normal tracer techniques utilizing

the addition of radioactive substances, the isotopetechnology provides another tracing method.This is based on the addition of a non-radioactivesubstance which can be determined subsequentlyby activation analysis. For such 'non-activetracers', elements are chosen which can be activatedgiving a high yield of radionuclides with suitablehalf-lives and radiation properties. The sensitivityof the activation analvsis makes this methodsuperior to conventionai combinations of tracersubstances and analytical techniques, but it ismuch more laborious.

The production of steel with the lowest possiblecontent of non-metallic inclusions is an importantand urgent task of modern metallurgy. Tracerand non-active tracer techniques have been usedto determine the source from where these inclu­sions penetrate into the liquid steel during smeltingand pouring. For this purpose, the lining of steelmelting furnaces and ladles as well as slag orany other suspected source is labelled with cSCamixed as oxide or carbonate in the lining material.The subsequent separation of inclusions from themetal produced, measurement of their radioactivityand autoradiography of the ingots give a directquantitative idea of the steel contaminationsources.

As non-active tracers, L~Os and DY20s havebeen used, as La and Dy have high activation cross­sections. Studies by Russian investigators haveshown that the exogenic inclusions are of minorimportance in killed steel, while they are mainlyresponsible for the inclusions in rimming steel.

IYA: APPLICATIONS OF RADIOISOTOPES IN METALLURGY IN INDIA

Non-active tracer technology has certain ad­vantages. On the one hand, it is advantageousin very large-scale investigations where it wouldbe complicated to handle the large amount of radio­activity needed; and, on the other, in investigationswhere a tracer is released in nature and the safetyof the public could not, with absolute certainty,be guaranteed.

Radioisotope Instruments

Radioisotope instruments like thickness, density,concentration and level gauges have enabled moderntechnology to derive great economic benefits. Theprinciple of these gauges is well known and dependson the interaction of the radiation emitted withthe materials being controlled, ie attenuation intransmission gauges or back-scattering of theradiation in back-scatter gauges. These radioisotopeinstruments are made up of (i) a radioactive source ­radiation detector system,the source and detectorbeing mounted with respect to the medium con­trolled; (ii) suitable electronics with a recordingunit; and (iii) a controlling or actuating unit.

The economic benefits derived from the use ofradioisotope gauges result from a number of factors.Their use increases plant efficiency, where theconventional process gauging is a bottleneck, de­creases the manpower necessary for monitoringthe process and accelerates analytical work.Savings in raw material and scrap are important,particularly where the raw material cost is a signi­ficant fraction of the final product cost. Finally,increased quality, the most quoted advantage ofnuclear gauging, makes the product more com­petitive.

The total number of nuclear gauges in all typesof industries in India is estimated to be less than200, as against an estimate of about 4000 gaugesin UK and about 10,000 in USA. The annualsaving from isotope gauging is estimated at about$ 50 million in USA in 1963 and at about $ 100million in the USSR in 1961 (ref 1).

It is estimated that in India about 120 nucleargauges have been installed in different metallurgicalindustrieS; of which nearly 100 are used for leveldetection in sintering plants and hot metal cupolas,the largest single user being the Bhilai steel plant.This includes about 50 level gauges. However, inthe field of thickness gauging, while these gaugesare considered to be efficient and economical inother countries, the benefits are yet to be recognizedin India. The thickness of even hot rolled steelin the range 4-100 mm is now being controlled byZITRA thickness gauges in the USSR. Iu thisgauge the radiation source is 137CS of 1 C strength,the detector being a scintillation counter with NaIcrystal. The detector set-up is water-cooled.Precision of the order of ±0'5% is claimed8.

The main users of thickness gauges are MessrsIndia Foils Ltd of Calcutta, where 10 beta raythickness gauges, using 2o'TI sources, measure thethickness of aluminium foils during the rollingprocess. These gauges cover the range 0·0002­0·02 in. with an accuracy of 1%. Besides these,it is understood that the Rourkela steel plant isalso planning to install thickness gauges for steel

[ ::=JTRONiCSFig. 1 - Schematic representation of the sample-source­

detector assembly in an X-ray fluorescence gauge

sheets during rolling and back-scatter gauges formeasuring the thickness of zinc coating.

A remarkable development in recent years hasbeen the growth of radioisotope instruments foranalysis, both in the laboratory and on-stream.They are now often used as an alternative to X-raymachines, .because they are smaller, cheaper andmore reliable. For instance, in isotopic X-rayfluorescence analysis, isotopes giving low energyy- and X-radiation can be used to excite charac­teristic X-rays of the element being sought in thesample.

X-ray fluorescence gauges (Fig. 1) are used formeasuring the thickness of metallic coatings liketin on steel, either by measuring directly the X-raysexcited in the coating or by measuring the absorp­tion (in the coating) of the X-rays excited in thebase material. In the case of Sn on steel, thick­nesses down to 0·1 I-'- can be measured. For gaugingZn on steel, suitable filters are used for energyselection.

In UK • dragonite' gauges are used in the SteelCompany of Wales, Port Talbot, for measuringthe thickness of electroplated Zn coating on steel,using a 3H/Zr source to excite the characteristicFe X-rays in the steel base, which are attenuatedby the Zn coating before detection by a scintil­lation counter. Zn thickness in the range 10-5­10-3 in. can be measured with 95% confidence toan accuracy of ±5% in 10 sec9. Apart from thoserequired for important on-line applications likeSn on steel and Zn on steel, most of the instru­ments have been designed to be portable to enablewide use in plant, laboratory and the field. Otherapplications are the continuous analysis of processstreams such as mineral slurries, and the field ana­lysis of metalliferous ores. The isotopes used oftenfor such applications are I09Cd (1·3 yr), 57CO (270days), 2uAm (470 yr), and 3H/Zr (12·3 yr). Thereis not a single X-ray fluorescence gauge in thiscountry, but one will soon be installed at BAReto demonstrate to the industry the wide utilityof such gauges and to explore the possibility ofdeveloping them indigenously.

19

Activation Analysis Techniques

A significant advance in metallurgy in recentyears has been the production of ultra-pure metals

J. SCIENT. nm. RES., VOL. 28, JANUARY 1969

by means of zone refining techniques. Metals usedin semiconductors must be free from certain impu­rities and must contain accurately known quantitiesof certain other elements. The influence of traceimpurities or of alloying elements upon the proper­ties of metals is of great theoretical and practicalimportance and radioactivation analysis has providedinformation in this direction which could not beobtained by any other method.

The principle of activation analysis is quite simple.The material under reference is subjected to neutronbombardment in a nuclear reactor; the mixtureof radioisotopes produced is analysed by gammaspectrometry directly or after suitable and rapidradiochemical separation. With activation ana­lysis, it is possible to determine concentrationsof 10-7 (ie 0·1 ppm) of rare earths, Sb, Mo andZn and 10-0 (ie 0·001 ppm) of Cu and As ingermanium. . .

A comparatively recent development m thiSfield is the portable neutron generator, in whicha stream of monoenergetic 14 MeV neutrons isproduced by bombarding the radioisotope tritium(3H) with deuterium (2H) ions. Such neutrongenerators have immense potentialities in themetallurgical industry and in particular in metal­lurgical analyses. Normally 3-5 C of tritium areadsorbed on zirconium targets and these are thenbombarded with deuterium ions accelerated to150-400 kV. Fluxes of 2-5 X 1011 neutrons/sec areobtainable. (The cost of such a generator wouldwork out to about Rs 3 lakhs.)

Oxygen in steel is an important contaminantthat must be determined rapidly and accuratelyduring production. Using neutrons from portableneutron generators, oxygen can be act!vat~d toform the radioisotope 16N whose determmatlOn ISthen carried out rapidly by gamma spectrometry.With neutron generators, large samples (up to 10 g)can be accurately analysed in half the time neededfor much smaller samples with other techniques.The system is non-destructive and the same samplecan be re-run if necessary.

At the steel factory at Cockerill-Ougree-Pro­vidence near Liege in Belgium, producing about2 million tons of steel per year, the oxygen contentin steel is determined by such techniques. It isclaimed that the analysis of each sample takesonly 2 min. One hundred and fifty samples, eachin triplicate, ie about 450 samples, are a.n~lyse.d

per day. At 20 ppm levels, 5-7% preclslO~. ISobtained, while at 1 ppm level, 20-30% preCISIOnis claimed [Personal communications, Messrs Sames,Grenoble, France).

Another field where neutron generators are findingincreasing application is neutron radiography. Thehigher transmission of neutrons through thick steel,lead, uranium and other heavy metals ~akes

this technique preferable to the conventIOnalX-ray and gamma radiography techniques in specificapplications. The technique of neutron. radIO­graphy is basically the same as gamma radIOgraphyexcept that, since neutrons have little effect onphotographic emulsions, indium foils placed close .tothe emulsions act as image converters. The radia­tions from indium are picked up by the emulsion

Analytical Techniques

There has been considerable progress in thisrespect on account of the de.vel?pments in radio­isotope methodology and their Impact on m~tal­

lurgy has been wide and useful. The technt<jueof isotope dilution is well known and the pnnclpleis simple. A known quantity of the actual sub­stance, labelled with a radIOactIve nuclide at aknown specific activity, is added to the sample.After equilibrium is reached, a samp~e of. the pro­duct is removed, weighed and its radIOactiVity andconsequently the specific activity determined.

Isotope dilution techniques have been used forthe assay of various constituents ~ike.Mo, W, Nband Ta in steello. In the determmatIon of phos­phorus, 32p is added to the melt in a suitab.le chemicalform. After it has mixed uniformly With all thephosphorus present, the phosphorus content ofthe steel and slag can be followed easily duringthe refining process. In one sample, the phosphoryscontent is determined chemically after the actIvityhas been measured. The activity of the steel andslag samples can then be used as a measure of thephosphorus content, using the chemically analysedsample as a standard. The measurement. can beperformed on site in the steel plant rapidly. Itis thus possible to determine the phosphorus contentof the slag, which is of value when the slag IS to beused as a fertilizerll.

Sulphur in steel and slag can also be determinedin the same way, but the method IS less attractIveon account of the soft beta radiation of sulphur. Iso­tope dilution techniques with tritium have also beenused for hydrogen determination in alu~iniumI2,13:

Using dilution techniques, it is pOSSible to weigheasily the amount of slag in open hearth furnaces.A known amount of a radioactive substance isadded to the slag phase, where it. rapidly ~issolves

in the molten slag. It then remams quantItatIvelyin this phase. The concentration of the added sub­stance is determined in samples and, from the result,the total amount of slag is calculatedl&. .

Dilution analysis can be performed With anysubstance that fulfils the metallurgical require­ments. The oxides of rare earth metals are usedas radioactive tracers. The choice of the rareearths for use as tracers is governed by their resis­tance to reduction - no risk of losses by transferinto the metallic phase exists. Radiotracer tech­niques using active BOLa and non-a.ctive tracertechniques involving activation analysIs are used.The amount of molten metal in an electric furnacefor the production of highly alloyed steels is mea­sured in Sweden on a routine basis with short-lived65Ni. The calculation for adding expensive alloy­ing compounds can be made with this method moreaccurately than is otherwise possible. The amountof molten aluminium in an electrolytic cell has beendetermined in the same way with 10BAu (ref 15). Itis also possible to use inactive gold and carry out thedetermination by subsequent activation analysisl6•

20

IYA: APPLICATIONS OF RADIOISOTOPES IN METALLURGY IN INDIA

which is then developed [personal communications,Messrs Sames, Grenoble, France).

Summary

Radioisotopes are being used at present in Indiain some metallurgical industries. mainly for qualitycontrol by non-destructive isotope radiographyand for gauging either the thickness of metal sheetsor the level of materials in closed vessels. Besidesthese, tracer inv~stigations of metal wear, wear ofrefractory linings, mixing of molten metals and diffu­sion phenomena have been carried out in some ofthe institutions. The present position in this re­gard is surveyed and the potential applications indi­cated, based. on the experience in other countries,on the use of radioisotopes in metallurgical researchand industry. These include recent developmentslike radioisotope tagging of steel. wear studies inmachines under actual working conditions usingdifferential radioactive tracer methods, radioreleasetechniques using 'kryptonated' solids, slag weightdeterminations by isotope dilution, measurementand analysis of thin coatings by radioisotope X-rayfluorescence gauges. routine analysis of oxygencontent at low levels by fast neutron activationanalysis using portable neutron generators andneutron radiography.

References

t _ f wiultrial radioisotope economics (International AtomicEnergy Agency. Vienna). 1965.

2. "\"EE". L. & FORSBERG. H. G .• Tekn. Tidskrift, 91(1961).671.

3. ERWALL. L. G .. FORSBERG. H. G. & LJUNGGREN. K.Proceedings of the seminar on ·practical applicationsof short·tived radioisotopes prodllced in small research

reactors (International Atomic Energy Agency, Vienna),1963, Vol 1. 229.

4. POSTNIKOV, V.I.. Proceedings of the symposiu", on radio­active tracers in industry and geophysics. Prague (lnter~

national Atomic Energy Agency, Vienna). 1966.5. FODOR, J., Proceedings of the symposium on radioactive

trace"s in industry and geophysics. Prague (InternationalAtomic Energy Agency, Vienna), 1966.

6. CHLECK. D., MACHL, R., CUCCHIARA, O. & CARNEVALE.E.. hzt. j. appl. Radiation Isotopes, 14 (1963),581.

7. CHLECK, D. & CUCCHIARA, 0., Int. j. appl. RadiationIsotopes. 14 (1963), 599.

8. Report 0" a study tour on 'Industrial application of radio­isotopes and radiation in Czechoslovakia, France, theSoviet Union and the United Kingdom' (InternationalAtomic Energy Agency. Vienna). 1967, 34.

9. Report Oil a study tow' on 'hzdllitrial application ofradioisotopes and radia.tion in Czechoslovakia, Fraflce.the Soviet Union and the United Ki"gdo",' (InternationalAtomic Energy Agency, Vienna). 1967, 72.

10. ALDIARIN, 1. P. & BILmOVITCH. G. N., Int. ]. appl.Radiatio" Isotopes, 7 (1960), 169.

11. FODOR. J. & VARGA. C .• Proceedings of the second UNinternational conference on the peaceful t'ses of atomicenergy. Geneva (United Nations, New York), 1958,Vol 19, 231.

12. GILLESPIE (Ir). A. S., Anal)'t. Chern .. 32 (1960), 1624.13. EVANS, C. & HETHERRINGTON, J., Proceedings of the

conference on the use of radioisotopes in physical sciencesand indltstry, Copenhagen (International Atomic EnergyAgency, Vienna), 1962, Vol 2, 309.

14. ERwALL. 1.. G. & LJUNGGREN, 1<.. Proceedings of thesecond UN international conference on the peaceflt/llsesof atomic energy, Geneva (United Nations. New York),1958, Vol 19. 3.

15. BOZOKY, 1.. & VODROS, D., Proceedings of the secondUN international conference on the peacef..l uses ofatomic energy, Geneva (United Nations. New York),1958, Vol 19. 237.

16. PRADZYNSKI, A. & ORMAN. Z.. Proceedings of the con­jereflee on the use oj radioisotopes in the physical sciencesand industry, Copenhagen (International Atomic EnergyAgency, Vienna), 1962, Vol 1. 477.

21

Some Aspects of Carbohydrate Metabolism In HaemoflagellatesD. K. GHOSH & A. G. DATTA

Indian Institute of Experimental Medicine, Caleu tta 32

ANTONY VON LEENWENHOCK, who forthe first time reported the occurrence offree-living fresh water protozoa, is commonly

recognized as the father of protozoology. Throughthe painstaking efforts of various investigatorsover the last 60 years, it has now been establishedthat some 25 species of protozoa occur in man.More recentl)!, interest has shifted towards studieson intermediary metabolism, with emphasis onthe enzymatic relationship existing between dif­ferent classes of protozoa and many other haemo­flagellates.

The main difficulty in pursuing the biochemistryof haemoflagellates is that only a few of the haemo­flagellates can be cultured in well-defined mediaoutside their hosts. Since successful metabolicstudies can be carried out only on species obtainedwithout contamination, such investigations havebeen confined largely to trypanosomes and themalarial parasites. A few haemoflagellates havebeen grown in pure cultural form and some in­formation regarding their growth and nutritionalrequirements has been obtained. The earliest ob­servation regarding the requirement of blood inhaemoflagellates was by Novy and McNeal' whoused blood-agar medium for the growth of Trypano­some lewisi and T. brucei. Subsequently, Nicolle2grew Leishmania tropica and L. donovani in thesame medium. Adler3 and Senekjie and Lewis4claimed the growth of various Leishmania andtrypanosomes on peptone medium enriched onlywith rabbit serum. But different groups of workershave established that no Leishmania or trypano­somes can grow in a completely haemoglobin-freemediumS-S. The requirement of haemin in thehaemoflagellates seems to be due to their inabilityto synthesize it9,lo. It seems that the Trypano­somidae have a tendency towards loss of syntheticability due to their parasitic mode of life and thishas not affected their survival.

Utilization of Different Su~ars inHaemofla~elIates

All defined media of trypanosomatids and mostundefined media contain a sugar. Glucose is mostfrequently used, but often sucrose at a proper pH(7'6-8'1) can replace glucose. Both glucose andsucrose are utilized for growth by all trypano­somatids growing in defined media at room tem­perature, but differences in utilization occur withrise in incubation temperaturell . The glucoseconsumption by the blood stream trypanosomeshas been determined in a number of organisms, vizT. lewisi'2 , T. evansi'3, T. brucei'4 ,IS, T. gambiense16

and with 11 species of African trypanosomes17 .

Glucose consumption by the cultural forms ofTrypanosomidae has been demonstrated withLeishmania and T. gambiense'8 and T. rhodesiense19 .

22

The intensity of sugar metabolism is higher inthe congolense, evansi and brucei groups than inthe Iewisi group'2-I4,18. Reiner and Paton20 andHawking21 found that African pathogenic trypano­somes consume sugar corresponding to 15-30%of their wet weight in 1 hr. There exists a definitedifference in carbohydrate requirement betweenthe blood stream form of African pathogenic try­panosomes and their cultural forms. Schern andBozzal022 found a small amount of stored glycogenin African trypanosomes, but Krijgman23 andMoulder12 found little indication of stored poly­saccharide.

Apart from glucose, fructose and mannose havebeen shown to be well utilized by various trypano­somatidases24-28. Pentoses and polysaccharidesare also utilized in some isolated cases. In manycases, maltose and saccharose are also utilized.Ryley29 has shown that the blood stream form ofT. rhodesiense can utilize glycerol, glucose, fructoseand mannose, whereas the cultural forms can utilizesome tricarboxylic acid cycle intermediates, espe­cially under acid conditions. Apart from glucose,fructose and mannose, glutamine can be well uti­lized by T. lewisi30 , whereas glutamate, glyceroland asparagine were shown to be utilized to a lesserdegree.

It has been observed that in L. donovani mannoseis utilized at a similar rate as glucose31. Thepresence of mannose phosphorylating enzyme andphosphomannose isomerase has been observed inthe cell-free extract of this organism. The utili­zation of ribose and galactose in this organism is10w32• The organism L. donovani has been shownto utilize sucrose well and the presence of a sucrosesplitting enzyme has been demonstrated33. Studiesby Chang" on four haemoflagellates (L. donovani,L. brasiliansis, L. tropica and T. cruzi) have shownthat the organisms can oxidize glucose and levulose,but not maltose and lactose.

End Products of Fermentation inHaemofla~elIates

The carbohydrate metabolism for all protozoais characterized by incomplete oxidations. Thisis well marked in the case of African pathogenictrypanosomes. It is a bit surprising that the Try­panosomatidae, though living in well-oxygenatedsurroundings, are characterized by incompleteoxidation. Hence, von Brand et aIM have classifiedthe Trypanosomatidae among the aerobic fermentersfrom the standpoint of metabolic types. Someof the trypanosomes and Leishmanias, in whichthe common Krebs cycle enzymes are lacking,should accumulate the end products of glycolyticcycle. In other parasites, however, such explana­tion does not always hold good. Thus, in theincubates of malarial parasites, lactic acid has been

GHOSH & DATTA: CARBOHYDRATE METABOLISM IN HAEMOFLAGELLATES

shown to be present, though they possess all theenzymes of the Krebs cycle36. Succinic dehydro­genase36 and another succinate splitting enzyme37are present in T. cruzi, yet in the incubates of theorganism succinic acid accumulates. In the intactorganisms either the enzymes responsible for theformation of succinic acid are more active thanthose related to its utilization or by some intra­cellular regulatory mechanism the latter are pre­vented from working at their maximum capacity.Excretion of organic metabolites is a highly uneco­nomic process, since a large part of the potentialenergy of the parent substance remains unutilizedby the parasite. This also may be the reason forthe trypanosomes needing large amounts of carbo­hydrates for their growth.

Pyruvate formation - Pyruvic acid is the mostimportant aerobic metabolic end product of bloodstream forms of pathogenic African trypano­somes36 ,39. Anaerobically, the excretion of pyruvateis reduced and part of the glucose carbon isaccounted for by glycerol.

Chang28 made an exhaustive study on the threespecies of Leishmania and T. cruzi and found thatappreciable amounts of succinic, pyruvic and lacticacids and carbon dioxide are produced by L. dono­vani. Fulton and ]oyner40 could not demonstratethe formation of pyruvic acid in this organism.But in a subsequent study, Crowther et al41 demons­trated the formation of pyruvic acid along withsuccinic and acetic acids in the culture medium.The formation of radioactive pyruvate32 has' beendemonstrated when cells of L. donovani are incu­bated in the presence of uniformly labelled glucose­14e. It has also been observed that the cellhomogenate of L. donovani produces lactic acidanaerobically. The formation of lactic acid isconsiderably diminished in the presence of iodo­acetate, but not in the presence of fiuoride42.

In T. equiperdum43, T. hippicum44 and T. evansi46,

glucose dissimilation proceeds up to the pyruvatestage, while with T. cruzi, T. lewisi, T. congolense,T. vivax and S. oncopelti, glucose degradation pro­ceeds beyond the pyruvate stage. This distinctionhas been clearly shown by Ryley", who studiedthe end products of both aerobic and anaerobicmetabolism of glucose in 11 species of trypanosomes.In six of the species, pyruvic acid and glycerol wereshown to be the end products and the respiratoryquotients in all these cases were very small. Work­ing with T. equiperdum, Reiner et al43 also madea similar finding. Pyruvic acid was also shownto be produced in T. evansi46•

Succinate formation - Succinic acid is the mostcommonly produced acid by the haemofiagellatesduring glucose catabolism; its production is oftenmuch more pronounced under anaerobic con­ditions17,29,46. Agosin and von Brand36 could notdemonstrate the formation of succinic acid underaerobic condition. Succinic acid was shown to beproduced in T. rhodesiense along with lactic, formicand acetic acids47. T. lewisi also produces succinic,pyruvic and lactic acids, besides several one- andtwo-carbon fragments43,48.

The formation of succinic acid aerobically maybe via acetyl CoA condensation and is an oxidative

process49. But succinate cannot originate underanaerobic conditions by the reactions of that cycleas they proceed under aerobiosis. Various path­ways leading to anaerobic succinate formationhave been suggested by different workers37 ,46,49,6o.Seidman and Entner60 suggested the anaerobicformation of succinate and pyruvate from malatein the presence of ADP and inorganic phosphate.Succinate formation has been noted upon anaerobicincubation of a particulate system from ascarismuscle with fumarate and reduced DPN61. Thisindicates the reversal of succinoxidase system, afeature possibly representing an adaptation to theworm's anaerobic life.

Most of the available evidence for the anaerobicformation of succinate in haemoflagellates is byreversal of some reactions of the Krebs cycle alongwith some auxiliary reaction, such as the formationof oxaloacetic acid. Oxaloacetic acid is generallyformed by carbon dioxide fixation. The impor­tance of transamination for the generation of oxalo­acetic acid cannot be assessed properly in theorganisms at present. First evidence for the fixationof carbon dioxide was provided by Searle andReiner48 ; it was confirmed by the manometricexperiments of Ryley". In the blood stream formof T. rhodesiense, the fixation of carbon dioxidewas demonstrated by the use of radioactive bi­carbonate. By the use of variously labelled glucoseand bicarbonate, Bowman et al46 demonstratedthat both aerobic and anaerobic formation of suc­cinate was due to carbon dioxide fixation to pyru­vate. The relative importance and distributionof the different carbon dioxide fixing enzymes, iepyruvate carboxylase, phosphoenol pyruvate car­boxylase, malic enzyme and other related enzymes,are not properly known in this group. However,Raw62 demonstrated the presence of malic enzymein T. cruzi. By the use of radioactive glucose andradioactive bicarbonate, it has also been foundthat in L. donovani carbon dioxide fixation takesplace during succinate formation. The presenceof malic enzyme has been found in the cell-freeextract of this organism, but the presence of phos­phoenol pyruvic carboxylase and phosphoenol car­boxy transphosphorylase could not be detected32.

Glycolysis in Haemofla~ellates

Studies made so far on the protozoal metabolismhave proceeded along two different lines. Thefirst concerns with studies on the overall metabolismof the entire organisms and the second involvesinvestigations on the intermediary metabolism re­quiring the preparation of cell-free extract. Fromsuch studies it appears that though the anaerobicsugar catabolism by the trypanosomes and otherprotozoa follows essentially the same pattern asfound in the majority of free-living organism, stillit has some differences and distinct characteristicsof its own.

There is evidence for the existence of modifiedglycolysis in trypanosomes. In normal glycolysis,pyruvic acid is reduced to lactic acid in the presenceof reduced DPN and thus maintains the supplyof DPN. But in T. brucei, glyceraldehyde phos­phate accepts the hydrogen of reduced DPN, a

23

GHOSH & DATTA: CARBOHYDRATE METABOLISM IN HAEMOFLAGELLATES

TABLE 2 - SOME ENZYMES OF THE KREBS CYCLEIN HAEMOFLAGELLATES

Hardly any work has been done so far on shuntpathway. Broad indications are provided for futurestudies in this field.

in great detail. The purified isocitric dehydro­genase of T. cruzi has been found to be TPN-linkedand to require Mn++ for its activity63. The succinicdehydrogenase of T. cruzi is essentially particle­bound and can function in the presence of cresylblue, but not in the presence of cytochrome c. Theenzyme could be inhibited by malonate, even ata very low concentration.

Apart from enzymatic studies, the detection ofKrebs cycle intermediates and their utilizationhave been taken as evidence for the elucidationof the cycle in different protozoa. In the culturalform of T. cruzi, almost all the intermediates ofTeA cycle can be utilized62• Similarly, Ryley29

has demonstrated the utilization of citric acid,",-ketoglutarate, and succinate in T. rhodesiense.In T. hippicum, the utilization of most of the Krebscycle intermediates could not be demonstratedt'oIt has been observed that in L. brasiliensis and inL. tropica, citrate, ",-ketoglutarate and succinatecan be utilized63•

Evidently, the demonstration of a few enzymesof this cycle or utilization of some of the inter­mediary substrates cannot be taken as conclusiveevidence for the presence of a complete cycle. En­zymes of the Krebs cycle may also be used for thesynthesis of amino acids or for some other processeshaving no connection with the terminal respiration.Similarly, it may be equally premature to assumethe absence of the cycle when the presence of afew of the enzymes could not be demonstrated orsome intermediates were not utilized. As it hasoften been found, difference in technique may leadto erroneous conclusions. In the case of utilizationof substrates the question of permeability is ofparamount importance.

In conclusion, it can be stated that a functionalKrebs cycle has not yet been demonstrated in anymember of this group of protozoa, with the samedefiniteness as in mammalian or bacterial systems.The cycle seems to be operated in cultural formsof most trypanosomids. It is expected to be absentin the blood stream forms of trypanosomes of bruceiand lewisi groups.

Summary

The work done to date on carbohydrate meta­bolism in the parasitic protozoa, haemoflagellates,has been reviewed. The haemoflagellates are wellmarked for incomplete metabolism and have beenclassified as aerobic fermenter from metabolic stand­point. Some scattered studies have been doneon Krebs cycle enzymes, but the presence of thiscycle in this group has not yet been fully established.

Enzyme

AconitaseIsocitric dehydro­

genaseFumaraseMalic dehydrogenase

Organisms

T. cruz·i. T. rhodesienseT. cruzi, T. lewisi, T. rhodesiense

T. CYuzi, T. rhodesie1tSeT. cruzi, L. donovani

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89. '8. SAITO, Y., J. Orient. Med., 26 (1937), 9.9. LWOFF, A., G.r. Seanc. Soc. Bioi., 113 (1933), 231.

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11. NATHAN, H. A., J. Protozool., 5 (1958), 194.12. MOULDER, J. W., J. infect. Dis., 83 (1948), 42.13. GEIGER, A., KUGLER, M. & CAMAROFF, R., Ann. trap.

Med., Parasitol., 24 (1930), 319.14. VON BRAND, 1'., Z. verg. Physiol., 19 (1933), 583.15. VON ISSEKUTZ, B., Arch. expo Path. Pharmak., 173

(1933), 479.16. VON BRAND, 1'., J. cell. compo Physiol., 31 (1948), 49.17. RYLEY, J. F., Biochem.J., 62 (1956), 215.18. VON BRAND, 1'., TOBIE, E. J., KISSLING, R. E. & ADAMS,

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49. SEAMAN, G. R., ]. bioi. Chern., 228 (1957), 149.SO. SEIDMAN, 1. & ENTNER, N., J. bioi. Chern., 236 (1961).

915.51. SEARLE. D. S. & REI"ER, L., J. bioi. Chern., 141 (1941),

563.52. RAW. 1.. Revla [nsl. Med. trap. S. Paulo. 1 (1959),

139.53. GRA"T. P. T. & SARGENT, J. R" Bioehem. ]., 76 (1960),

229.54. GERZELI, G., Riv. Parasil .. 16 (1955), 209.55. CHEN, G. & GEILLING. E. M. K.,]. infeel. Dis., 77 (1945),

139.

56. CHEN, G., J. infect. Dis., 82 (1948), 226.57. CHRISTOPHERS, S. R. & FULTON, J. D., Ann. Irop. Med.

Parasil., 32 (1938), 43.58. BAERNSTElN. H. D. & REES. C. W., Expl Parasit., 1

(1952). 215.59. RYLEY, J. F .. Nalure. Land., 171 (1953), 747.60. CHATTERJEE, A. N. & GHOSH, J. J., Nature, Land., 182

(1958), 109.61. VON BRA"D, T. & AGOSlN, M., J. infect. Dis., 97 (1955).

274.62. AGOSIN, M. & WEINBACH, E. C., Bioehim. biophys. Acta,

21 (1956), 117.63. MEDINA. H., AMARAL, D. & BAClLA, M., Arquiv. Bioi.

Teenol., lnst. Bioi. Pesquisas Teenol., 10 (1955), 103.

Steroid Saponins of Some Indian Plants·R. N. CHAKRAVART1t. (Mrs) D. CHAKRAVARTq, (Miss) SIBANI DATTA & & M. N. MITRA

Department of Chemistry, School of Tropical Medicine, Calcutta

THE research activity on steroid sapogeninswas intensified after the discovery of thebeneficial effect of cortisone by Kendall and

his coworkersl . Particular mention may be madeof Marker et al2-4 for their pioneering efforts in thisfield. In recent years considerable attention hasbeen focused on the conversion of steroid sapogeninsinto useful steroid honnones. The work carriedout in India on survey and isolation of steroid sapo­nins by the authors has been reviewed in thiscommunication.

With the object of exploring the possibility ofproducing steroid hormones in the country, a surveyof the Indian Dioscorea yams (Fam: Dioscoreaceae),commonly known as jungle roots, was undertakenaround 1950. The yams, collected mostly throughthe courtesy of forest officers, were investigated5-u .The yams of Dioscorea prazeri Pr. and Burk. (kukurtoml) of Darjeeling area and D. deltoidea Wall. (kins)of Kashmir were found to be rich sources of dios­genin, a steroid sapogenin useful as a startingmaterial for the preparation of a number of steroidhonnones including cortisone. Using diosgenin,it was possible to prepare a number of steroidhormones, including progesterone, for the first timein Indial3. Laevulinic acid" was obtained in con­siderable amounts as a useful byproductl5 duringhydrolysis of Dioscorea saponin into diosgenin. Itis formed obviously by the action of hot hydrochloricacid on the sugars of the saponin and the largequantities of starch present in the yams.

Dioscin was isolated by Tsukamoto and Ueno lO

as the chief saponin of Dioscorea tokoro Makino.Later, D. gracillima17,l8 yielded gracillin along with

• Paper presented at the Symposium on Glycosides andSaponins held in Calcutta during 2-4 April 1964.

tPresent address: Indian Institute of Experimental Medicine,Calcutta.

tPresent address: Department of Chemistry, BethuneCollege, Calcutta.

26

dioscin. Barua et alIe isolated pure crystallinesaponins from Indian dioscoreas, D. prazeriand D. deltoidea. The saponins on hydrolysis with6% hydrochloric acid yielded diosgenin, glucoseand rhamnose20•

The saponin obtained from D. prazeri, mp 276-7°(decomp) [OC];2 _900 (pyridine) and that from D.deltoidea, mp 288-90° (decomp) [oc]~2-95° (pyridine)had different solubilities21 and appeared to be dif­ferent from each other. The identities of these withdioscin16 and gracillin'8 have not yet been estab­lished, although the saponins obtained by theauthors yielded rhamnose at the end of the chainof sugars as in the cases of dioscin and gracillin.

Yams of D. prazeri var glauca also yielded a crys­talline saponin which was found to be practicallyidentical with that of D. prazeri.

In view of the presence of physiologically activealkaloid in the stems and leaves of Cestrumparqui!2,U, the investigation was extended to theCestrum species in India. The leaves of Cestrum1tOcturnum (Fam: Solanaceae) (night jessamine orhasna-hena) have been found to be rich in saponin.On fractional solvent extraction they yielded amixture of saponins from the alcoholic extract.The product after repeated crystallizations wasstill found to be a mixture, mp 260-69°, [oc];2_57°(pyridine). It gave a beautiful purple colourationwith concentrated sulphuric acid and on hydrolysisyielded a mixture of yuccagenin and tigogenin.These two were separated by chromatography overBrockmann alumina when tigogenin was obtainedby elution with a mixture of benzene and ether,and yuccagenin by elution with absolute alcohol.Tigogenin and yuccageninU thus obtained werepurified by crystallization and their identity estab­lished by the melting points (207-8° and 242-3°Crespectively), preparation of the derivatives, tigo­genin acetate (mp 200-201 0C), tigogenin benzoate(mp 228°C), tigogenone (mp 204°C), yuccagenin

CHAKRAVARTI el al: STEROID SAPONINS OF SOME INDIAN PLANTS

acetate (mp 178-9°), yuccagenin benzoate (mp 220­22°) and by comparison of infrared (IR) spectra.

The sugars produced by hydrolysis of the mixturewere found to be xylose, glucose and galactose bypaper partition chromatography using ethyl acetate­pyridine-water as the eluent. It may be quitelikely that the saponin mixture consists of tigoninand yucconin.

The plant Cestrum diuY1lum (Fam: Solanaceae),a plant similar to Cestrum noctunmm, grows wildin abundance throughout the country. The leavesof the plant yielded, on fractional solvent extraction,ursolic acid26 in the ether extract and a crystallinesaponin, tigonin2e, in the alcoholic extract. Onhydrolysis, the saponin yielded tigogenin. Thepresence of xylose, glucose and galactose wasestablished with the sugar part of the saponin bypaper partition chromatography. The position ofxylose in the chain of sugar units could be indicatedby partial hydrolysis at a point farthest from thesapogenin residue. In other words, the saponinconsisted of one tigogenin molecule attached toxylose molecule through glucose and galactosemolecules.

Pharmacolo~ical Studies

Pharmacological examinations of the purifiedcrystalline saponins obtained from D. deltoidea (D),D. prazeri (P) and D. prazeri var glauca (G) werecarried out at the Central Drug Research Institute,Lucknow (Mukerji, B., private communication).Saponins P and G, which are soluble in propyleneglycol, produced a fall of blood pressure of about45 and 25 mm of Hg respectively in anaesthe­tized cats when given intravenously in a dose ofO'5 mg/kg. This fall of blood pressure could beprevented by atropinization. Saponin D beinginsoluble in propylene glycol, its suspension in pro­pylene glycol was used. There was no effect onblood pressure when it was given intravenouslyin the same dose. Further, these drugs had noaction on isolated guinea-pig ileum.

It may be mentioned that the saponin from aCaucasian Dioscorea yam27 (D. caucasia, Lipsky?)has been found to be useful in USSR in cases ofatherosclerosis, particularly cerebral atherosclerosis.This may probably be explained as being due tothe removal of the deposited cholesterol by complexformation with the saponin.

Pharmacological examination of the saponin fromthe leaves of Cestrum nocturnum showed2e that thesaponin possesses cardiac activity similar to thatof ouabain.

Summary

The work done by the authors on survey andisolation of steroid saponins from Dioscorea and

Cestrum species, and pharmacological examinationof the saponins have been reviewed.

Acknowled~ement

Thanks are due to the Council of Scientific &Industrial Research, New Delhi, and Messrs GlaxoLaboratories (India) Private Ltd, Bombay, forresearch grants.

References

I. MASON, H. L., MYERS, C. S. & KENDALL, E. C., J. bioi.Chem., 156 (1936), 267.

2. MARKER, R. E. & ROHRMANN, E., ]. Am. chem. Soc., 62(1940), 518.

3. ~iARKER, R. E., TSUKAMOTO, T. & TURNER, D. L., J. Am.chem. Soc., 62 (1940),2525.

4. MARKER, R. E .• WAGNER, R. B., ULSHAFER, P. R.,WITTBECKER, E. L., GOLDSMITH, D. P. J. & RUOF,C. H., J. Am. chem. Soc., 69 (1947), 2167.

5. BARUA, A. K, CHAKRAVARTI, R. N. & CHAKRAVARTI,pirs) D., Indian med. Gaz., 88 (1953), 422.

6. BARUA. A. K, CHAKRAVARTI, (Mrs) D. & CHAKRAVARTI,R. N., J. Indian chem. Soc., 31 (1954), 173.

7. BARUA. A. K, CHAKRAVARTI, (Mrs) D. & CHAKRAVARTI,R. N., Bull. nal. Insl. Sci. India, (No.4) (1955),15.

8. CHAKRAVARTI, R. N., J. Instn Chem. (India), 27 (1955),108.

9. BARUA, A. K., CHAKRAVARTI, (Mrs) D. & CHAKRAVARTI,R. N., ]. Indian chem. Soc., 33 (1956), 799.

10. CaAKRAvARTI, R. N., CHAKRAVARTI, (Mrs) D. & MITRA,i\L N., j. Instn Chem. (India), 31 (1959), 218.

11. CHAKRAVARTI, R. N .. CHAKRAVARTI, (Mrs) D. & MITRA,M. N., J. Indian chem. Soc., 38 (1961), 635.

12. CHAKRAV.<RTI, R. N., Sci. Ctllt., 28 (1962), 151.13. CHAKRAVARTI, R. N .• CHAKRAVARTI, DEBI & MITRA,

M. N., Bull. Calcutta Sch. trap. Med., 5 (1957), I.14. CHAKRAVARTI, R. N. & DATTA, (Miss) GITA, J. 11lStn

Cllem. (India), 30 (1958), 276.15. CHAKRAVARTI, R. N., CHAKRAVARTI, (Mrs) D. & MITRA,

M. N., J. Insln Chem. (India), 32 (1960), 22.16. TSUKAMOTO, T. & UENO, Y., J. pharm. Soc. Japan, 56

(1936), 802.17. TSUKAMOTO. T. & KAWASAKI, T., J. pllarm. Soc. Japan,

74 (1954), 1127.18. TSUKAMOTO, T., KAWASAKI, T. & YAMAUCHI, T., Pllarm.

Bull., Tokyo. 4 (1956). 35.19. BARUA, A. K, CHAKRAVARTI, (Mrs) D. & CHAKRAVARTI,

R. N., Bull. Calctltta Sell. trap. Med., 3 (1955), 15.20. CHAKRAVARTI, R. N. & DASGUPTA. B., J. hlstn Cllem.

(India), 27 (1955), 177.21. CHAKRAVARTI, R. N., MITRA, M. N. & CHAKRAVARTI,

DEBI, Btlll, Calctltta Sch. Irop. Med., 11 (1963), 20.22. The wealtll of India. Vol 11 (Council of Scientific &

Industrial Research, New Delhi), 1950, 125.23. SILVA, M., MANCINELLI. P. & CHEUL, M., J. Am. pharm.

Ass. (Sci. Edn) , 51 (1962), 289.24. CHAKRAVARTI, R. N., DATTA, (Miss) SIBANI & MITRA,

M. N .• Btlll. CalctlUa Scll. trap. Med .• 11 (1963),56.

25. CHAKRAVARTI, R. N., DATTA, (Miss) SIBANI & MITRA,M. N., Bull. Calcutta Sch. trop. Med., 11 (1963),20.

26. CHAKRAVARTI. R. N., DATTA, (Miss) SIBANI & MITRA,M. N., Bull. Calcutta Sch. trap. Med., 10 (1962),123.

27. Indian J. Pediat., 27 (1960), 264.28. Roy, A. & CHATTERJEE, M. L., Bull. Calculla Scll. trap.

Med., 11 (1963), 156.

27

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MECHANICS byPublishing Co,Pp viii+132.

THE PHILOSOPHY OF QUANTUMD. T. Blokhintsev (D. ReidelDordrecht, Holland), 1968.Price Dfl 32

The present monograph is devoted to a critique ofthe philosophy of quantum mechanics. It is moreconcerned with theoretical physics rather than philo­sophy. Determinism which has been the basis ofclassical physics is illusionary, because the basicassumption that it is possible to determine uniquelythe future state of a system from its initial data isbased on an abstraction which does not includerandomrress. But the effects of randomness cannotbe disregarded in the general case, because theuncertainty arising from the initial data increaseswith time and the prediction becomes meaninglessafter a lapse of a certain finite time. Howeversmall the random deviations in the initial data orrandom forces may be, their consequences alwayspredominate after some time. This is in particulartrue for a system with large degrees 0 f freedom.When a large number of random factors dominate,a new law' the statistical regularity' emerges.According to Gibbs, a large number of identicaland completely mutually isolated systems, each ofwhich interacts weakly with a large macroscopicsystem at a set temperature (an ensemble), de­scribe the thermodynamic behaviour of the systemin terms of a canonical probability distribution,which gives a completely definite value for anythermodynamic measurement.

Quantum mechanics is essential to explain thezero-point energy of a system at absolute zero, asis shown by experiments on light scattering due tothermal motion at low temperatures and at abso­lute zero. Thus, a Gibbs ensemble spontaneouslybecomes a quantum ensemble at absolute zero.A very important characteristic feature of a quan­tum errsemble is Heisenberg's uncertairrty principle.In fact, we can defirre the totality of systems irrwhich the uncertainty principle holds as a quantumensemble.. Such an ensemble can be described interms of a wave function tV or a density matrix P.Using the Heisenberg relation or Bohr's principle ofcomplementarity it can be shown that this wavefunction can be a function of either the coordinatesor the momenta describing the system. Both tVand P satisfy differential equations which expresscausality in quantum mechanics. The principle ofsuperposition of states plays a fundamental part inquantum mechanics and the symmetry conditionsfor a system of identical particles can be con­veniently incorporated in the theory. One cannot,therefore, consider quantum mechanics as a form ofclassical mechanics supplemented by some quantumforce, because any such attempt faces serious obs­tacles, as it employs, in one way or the other,equations which are nonlinear with respect to thewave function. Moreover, the wave function canbe measured. For instance, in the simple case ofbound states of an atom, the amplitude can be

28

measured in terms of the mean particle density andthe phase can be measured by the magnetic momentof the atom. In general, the wave function can bemeasured by the differential cross-section for elasticscattering of probe particles.

The usual problem in quantum mechanics is thatof finding the eigenfunctions and the correspondingeigenvalues of the Hamiltonian of the systems.The inverse problem is to find the Hamiltonian fromthe experimental data on the energy states and thecorresponding eigenfunctions. A method for find­ing the potential function is given and illustratedby reference to scattering in the 5 state for a sys­tem. But the method is, in general, not of muchpractical importance.

There is a detailed discussion on the role of themeasuring instruments in quantum mechanics. Theoutput of any instrument is always a macroscopiceffect, eg deflection of a pointer in a metre, forma­tion of droplets in a Wilson cloud chamber, blacken­ing of grains in a photographic emulsion, etc.Thus, we use a macroscopic instrument to measurea microsystem. A detailed analysis is given of theaction of the measuring instrument both as an ana­lyser of a quantum ensemble and as a detector ofindividual events. It is shown that a macroscopicmeasuring instrument must be an unstable system,for only then a microparticle can alter its state andthis change of state is a macroscopic event. Amicroparticle is powerless to act as an instrumentrepresented by a stable macroscopic system; forinstance, it cannot displace the pointer from thezero position. The observer himself does not getinvolved in any measurement.

Einstein gave an example, known as Einstein­Rosen-Podolski paradox, to show that quantummechanics is not a complete theory. It was shownby Bohr and later by Mandelstam that the argu­ments given in the example regarding the possibi­lity of simultaneous measurement of the coordinateand momentum of a particle are falacious, becausethey contradict the principle of complementarity.The problem of latent parameters in quantummechanics is then discussed and it is shown that itis impossible to introduce latent parameters whichare, in principle, observable without causing aconflict with the principle of complementarity.However, this does not rule out the presence ofunobservable latent parameters. An example isgiven to illustrate the point. Further, the indivi­dual history of a particle can be given as a sequenceof macroscopic events; for instance, the history of an-meson which collides with a proton and so gene­rates two new n-mesons in a bubble chamber. Oneshould not hope for a more detailed description ofthe events, for each bubble in the bubble chamberreflects a catastrophe in the microcosm. We cannotpoint to a single experimental fact that would indi­cate that quantum mechanics is incomplete withinthe range of atomic phenomena of the microcosm.

F. C. AULUCK

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SEIIIIMICRO QUALITATIVE ANALYSIS by F. J. Welcher& R. B. Hahn (East-West Press Private Ltd,New Delhi), 1968. Pp x+497. Price Rs 10.00

A book of the above title is expected to emphasize thepractical schemes of qualitative analysis embracingall the common and many of the rare elements.But the present edition falls short of this expectation.The authors have divided this work into three parts,namely Part 1: Theory; Part II: Reference; and PartIII: Experimental. Part I comprises 15 chapters,Part II, 11 chapters (16-26 both inclusive), andPart III, 15 chapters. The importance given to theanalytical part itself is very much diluted.

A book on qualitative analysis should aim atproviding analytical chemists with proper backgroundof theory rather than help produce laboratorytechnicians and, therefore, any book on the subjectshould necessarily include chapters on theory pertain­ing to that branch of analysis. However, aftergoing through Part I of the present work, it isobserved that many of the chapters in it are notdirectly relevant to the title of the book. Chapters1-4,9, 14- and 15 will be more appropriate in a bookon general chemistry, dealing with volumetric, gravi­metric and physical chemistry experiments. Chap­ters 10 and 12 could as well have been included assubtitles of Chapter 8. Inclusion of not very relevantchapters further depreciates the value of the work.

In Part II, Chapters 16 and 17 are tables, whichare useful for analytical chemists in general. Chapter18 on mathematical operations has been written withcommendable simplicity and it will be very usefulfor quantitative analytical Chemistry students ratherthan semimicro qualitative analysis workers. Apartfrom these three chapters, the other chapters (19-26)deal with the properties of metals and their ions.Their placement under Part II is of doubtfulexpedience. A better arrangement would have beento include the material of the latter chapters underPart III in appropriate chapters like 30, 31, etc.Also, the following material could have been broughtunder Part II: Table 5 (p 15); Table 9 (p 24);Tables 16 and 17 (p 39); and Table 22 (p 54);all these are useful for general analytical chemists.

The authors claim to deal with the' large semi­micro scale' (preface, p v). This is a new coinageby the authors, as there is no such division aslarge and small semimicro scale. On going throughthe volumes and quantities n;commended for workin the book, the procedures seem to be more or lesson a macroscale. One feels that the title of the bookis a misnomer as compared with the books of Holnessand Belcher.

Semimicro analysis is of special significance inmodern analytical chemistry, as it introduces ascheme for the detection of rare elements. Completeexclusion of the rare elements with the exception oftitanium limits the usefulness of this book con­siderably. Description of the apparatus and tech­niques used in semimicro analysis given in Chapter27 is very inadequate. Companies like BDH haveput in the market semimicro kits (known as ' Meso­chemical analytical kit ') comprising a set of usefulapparatus and organic reagents for confirmatorytests. In the light of these developments, Chapter27 is inadequate.

Advantages claimed in page vi of the prefaceare of doubtful usefulness. Holness and Trewick'smethod using Li(OH) and KN08 is not advisable forAsian laboratories, as Li(OH) is several times costlierthan NaOH. Moreover, sodium hydroxide worksas well in the separation of elements of groupII A and B.

On page 386, the authors proceed to precipitatemembers of groups III and IV of the regularqualitative analysis collectively as mixed hydroxidesand sulphides. The advantage of this mixed preci­pitation procedure is very doubtful. It has definitedisadvantages, such as (i) having to do an additionalseparation, and (ii) creating confusion in the mindsof students who have been already trained in theregular qualitative analysis, because groups IV and Vof the authors correspond to groups V and VI ofthe conventional qualitative analysis. (Vogel isprobably the inspiration for the authors in thisrespect.)

Willard and Goodspeed's nitric acid method for theseparation of calcium and strontium adopted by thepresent authors seems to be elusive, since even asmall quantity of water on the semimicro scale maygive negative result.

On page 413, the authors admit that spot tests arenot given prominence in this work, and, in fact, theymake use of only' three organic reagents' (preface,p vi), namely dimethyl-glyoxime, Aluminon andMagneson. No doubt, organic reagents are vulnerableto interferences, but a large number of precise testsunder controlled conditions are possible in semimicroanalysis with the help of 20-25 reagents. This againis a point of deficiency in the book.

The applications of hydrolysis in analytical chemis­try given under 'Principles of hydrolysis' are toofar fetched and unusual to be of any practicalnecessity. No doubt, they are interesting examplesto enrich the theoretical background.

The questions and worked-out problems at theend of each chapter are commendable. Lucidity ofexpression and presentation show the experienceof the authors as teachers. Figs. 6-8 in Chapter 3are specially commendable. Figs. 18 and 19 onpages 165 and 166 respectively giving the electronicconfiguration for the tetrahedral, both as Sp8 andd8spa, are confusing; d8sp8 corresponds to fcoctahedron. Para 174 on page 172 gives twoformulae for the product of reaction of ferric ion withthiocyanate, [Fe(CNS)a]8- and [Fe(CNS)]2+, which areagain confusing in the absence of correct depictionof conditions. On page 175, the inclusion of NH,radical along with aquo complexes is misleading.NHa can form NH, radical not only with water butalso with any protonic acid. The authors could haveadhered to the conventional way of representingelectronic configuration, eg on page 244, 6s26P6pcould have been better represented as 6s26p2 or6s26p.6Py. The same remark will apply to otherinstances in the book (eg pp 253 and 264).Similarly, the structure of oxygen as an example ofdouble bond given on page 13 is also not satisfactory.At times the oxygen structure is also :O~ 0:to explain its paramagnetism. Ethylene or carbondioxide would have been a better example of doublebond.

29

J. SCIENT. IND. RES., VOL. 28, JANUARY 1969

In the tables depicting complexes (eg on pp 244,248, etc) the coordination number and the oxida­tion states could also have been included as twoadditional columns. In page 252, the expression, dissolves giving colourless solution' would have readbetter than 'dissolved with colourless solution'.This error has been repeated in other places also(eg on p 254, Table 35). 'The analysis of thegeneral unknown' is a repetition of the materialgiven on page 418 and hence it is superfluous. Inpage 432, under flame test, colours of the flamesfor a few common ions could have been given.Under ammonia test (p 437), the hanging-dropcell method could have been indicated. Chapters39 and 40 could have been amalgamated. There arequite a few printers' devils at various places.

To summarize, the material inside does not justifythe title given to the book. The authors havedissipated their energies in too many theoreticalchapters, which are not directly useful for semimicroqualitative analysis. Analytical (practical) part hasbeen presented in a rather diffuse form. If the bookis aimed at helping semimicro analytical students,it definitely fails in the purpose. It cannot be saidthat it has added anything more to the technique ofsemimicro analysis than what has been done byHolness, Vogel and Belcher.

However, it should be admitted that many of thechapters given under Part I will be of immense useto the general chemistry students. The authors havemeticulously represented all equations in ionicforms as befitting modern theories. The theoreticalchapters are very lucid, which any student canfollow unaided. Several questions are presentedat the end of each chapter. Worked-out examplesprovided will be of great help to the concernedstudents, though not to the students of semimicroanalysis.

P. B. JANARDHAN

MEDICINAL PLANTS by S. K. Jain (National BookTrust, India, New Delhi), 1968. Pp xii+176+plates: black and white, 29 and coloured, xii.Price Rs 5.75

This book is the latest in the series 'India - TheLand and People' being brought out by theNational Book Trust, India. As the author says inhis introduction, the purpose of the work is 'not toprepare a book of prescriptions for different diseasesbut to apprise the reader with some of the morecommon reputed medicinal plants of India'. Some80 plants have been dealt with in as many chapters.The trade name or the most common name of thedrug forms the title of the Chapter. The botanicalname, common names and botanical description arefollowed by the most important part of the chapter- that dealing with the properties of the drug andgiving all the uses which it finds in the traditionalsystems of medicine and folklore.

The book is a valuable addition to the series.The value of the book to all classes of users as apopular handbook would, however, have been en­hanced if the author had identified under each drugthe properties and uses substantiated by chemicalinvestigations or mentioned in one or the other ofthe pharmaceutical codices so as to separate them

30

from the other uses which could be attributed toindigenous system or folklore only. Further, itwould perhaps have been quite profitable if a quali­fied medical man conversant both with allopathicand ayurvedic/unani systems were also associatedwith the author in compiling the sections dealingwith medicinal uses for a critical assessment of themedical literature on the subject. Thus in page57, Embelia tsjeriam-cottam is said to be 'effec­tive only against tapeworms, and not hookwormsand roundworms', but in the very next sentencewe are told that 'it should be useful in ascariasis'.Ascariasis is, as we know, the medical man's termfor roundworm infestation.

In spite of the seeming profusion of text-figuresand also black and white and colour plates in thebook we find that some 30 out of the 80 plantsdealt with are not illustrated at all and thisreduces the utility of the book to that extent. Forexample, there is no illustration of Ocimum sanctumand that of O. Kilimandscharicum is so poor thatit could well have been omitted. The illustrationof Ephedra gerardiana is also very poor and showsmore rock and soil than plant. A reference toappropriate text-figure or plate should have beengiven in each chapter. The botanical name of eachplant should have been given in parentheses afterthe title of each chapter in the contents page, parti­cularly since the serial arrangement of the chaptershas been based on the alphabetical order of thebotanical name of the drugs.

R. S. CHAKRAVARTHY

ANIMAL GAMETES (FEMALE) by Vishwa Nath (AsiaPublishing House, Bombay), 1968. Pp xix+ 195.Price Rs 60.00

Like its predecessor, Animal gametes lMale) , thepresent volume is yet another monumental contri­bution by Dr Vishwa Nath, the pioneer animalcytologist of the country. It is devoted primarilyto a morphologic and cytochemical account of yolkformation during oogenesis in invertebrate (insects,spiders, crustacea) and vertebrate (fishes, amphibiaand mammals) forms, based mostly on outstandingresearches by the author and his associates. Theclassical cytologic techniques and the recentsophisticated cytochemical and electronmicroscopicprocedures have been used judiciously and perti­nently to elucidate t!le morphology, ultrastructureand cytochemistry of organelles (nucleolar extru­sions, yolk nucleus, mitochondria, Golgi complex,vacuome and the endoplasmic reticulum) involvedin vitellogenesis. Particular attention has beenpaid to synthesis of protein yolk by RNA-richnucleolar extrusions, mitochondria, yolk nucleusand the endoplasmic reticulum. The role of Golgicomplex in biogenesis of yolk triglycerides has like­wise been described in detail.

The presentation of the textual matter and theillustrations are superb and the coverage of litera­ture has been extensive. The treatise will be avaluable source of information to the cytologistspecially interested in female gametes. Dr VishwaNath deserves our gratitude for this excellent,scholarly and timely treatise.

A. B. KAR

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ORGANIC FUNCTIONAL GROUP ANALYSIS: Vol 8, byF. E. Critchfield (Pergamon Press Ltd, Oxford),1963. Pp vii+187

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31

NOTES & NEWSLasers for measurin~ rates ofultra-fast chemical reactions

A laser beam has been provedby workers at the University ofCalifornia to be superior to anultrasonic probe for determiningthe rates of ultra-fast chemicalreactions. The analysis of re­actions, occurring within 10-12 sec,may now be possible by measuringthe quasielastic scattering of laserlight by salt solutions. Evenwhen the solutions are at equi­librium, as far as temperature,pressure and concentration areconcerned, they are never entirelyfree from minute local fluctuations.The return to equilibrium of thesespontaneous fluctuations involves arelaxation time that is character­istic of the kinetics of the system.

The new technique depends onthe Doppler broadening of thelaser wavelength caused by loca­hzed fluctuations in the solutionsthrough which the laser passes.The degree of wavelength stretchis a measure of the rate of thechemical reaction. Due to thegreat 'purity' attainable in alaser beam, it is possible to detecta wavelength spread of even onepart in 10 million A.

This laser technique can beapplied to a variety of ultra-fastchemical reactions, such as thoseinvolving proton transfer. Itshould enable biochemists, forexample, to gain insight into themechanistic details of enzyme­initiated processes [Chem. EngngNews, 46 (No. 29) (1968). l4J.

Meltin~ point determinationby NMR

A new method for observingmelting and determining meltingpoints, utilizing the motional nar­rowing of the NMR line at thephase transition, has been deve­loped. Impurity premelting takesplace during the melting processin any real substance. This pre­melting helps the observation of aspin echo signal immediately belowthe melting point.

Impurity premelting, also knownas two-phase premelting or Raoult

32

premelting, arises from the pre­sence of impurity centres distri­buted throughout the solid sample.In the immediate vicinity of theseimpurity centres, the melting tem­perature is lower than that forthe pure substance. As thetemperature is increased, more ofthe substance melts until theapparent melting point (Tm)A isattained. At this point, the entiresample is liquid.

According to the Raoult theoryof impurity premelting, the frac­tion of the sample which is liquid,A (T), at any temperature T belowthe apparent melting point, isgiven by the equation

A(T) = rI+(T~)A-Trwhere !:J. is the difference betweenthe true meltin~ point Tm and theapparent melting point (Tm)A.

With the aid of pulsed NMR,the liquid fraction of a sample ismeasured as a function of tem­perature in the premelting region.This new method of melting pointdetermination is applicable, inprinciple, to any substance con­taining nuclei with spin greaterthan zero. To measure this liquidfraction, a spin echo is producedby placing the sample in a magne­tic field and irradiating it withtwo radio frequency pulses a timeor apart at the Larmor frequency.The echo, of amplitude A, appearsat a time 20r after the first impulse.The echo amplitude depends onn, the number of spins contribut­ing to the signal. It can be shownthat the spin echo amplitude inmost cases depends on n, thenumber of spins in the liquidenvironment, so that A is directlyproportional to the liquid fractionA(T).

Two samples of ethane wereused to demonstrate the abovemethod. The first sample had apurity of not less than 99'96%,and the second not less than 99%.The echo spin amplitude wasobserved for both cases as afunction of temperature between88·8° and 90·2°K. It was found,after making the necessary cal­culations, that the estimation of

the true melting point in thetwo cases agreed very well. Thetemperature control in this experi­ment was done using a liquidoxygen bath, the melting pointof ethane being close to the boil­ing point of oxygen. A platinumresistance thermometer calibratedby the National Bureau of Stan­dards was put next to the sampletube and both were placed in acopper case to minimize tempera­ture gradients. The vapour pres­sure over the bath was controlledto ± 0·1 mm of mercury by aCartesian manostat. The twocommonly quoted values for themelting point of ethane are89·89° and 90·35°K. The abovemethod yielded the value 89·82°K,consistent with the first one[Nature, Lond., 219 (1968), 59].

A new synthesis ofaromatic and aliphaticcarboxylic acids

A new synthesis of carboxylicacids by a Pd(II)-catalysed carbonmonoxide insertion, which takesplace under mild conditions with avariety of metal aryls, has beenreported. These metal aryls reactwith Pd{II) under carbon mono­xide atmosphere to give palladiummetal and acid chlorides. Thus,phenyl mercuric chloride reactswith Pd(II) chloride in CHaCNunder atmospheric carbon mono­xide pressure at 25°C to givebenzoyl chloride according toEq (I)

CH.eNC6H,HgCl+PdCI2+CO --....

C.H,COCl+Pd+HCl ... (1)This reaction probably proceeds

by way of an unstable aryl palla­dium compound which insertscarbon monoxide followed by de­composition of aryl compound togive acid chloride.

C6H6HgCl+PdCI2 -+co

HgCI2+[C6H,PdC1J -....

oII

[C6H,C-PdCII-+ C6H,COCl+Pd

Esters are obtained using al­cohols as solvent. Pd{II) catalystmay be regenerated by reactionwith CuCI2• In some cases diarylketones and coupled products areobtained as side products. Thecorresponding alkyl metal com­pounds react to give aliphatic

carboxvlic acids. The reaction isapplicable in those cases alsowhere mercury aryls have beengenerated in situ [Tetrahedron Lett.,(No. 19) (1968). 2285).

A new oxytocic substancefrom ox hypothalamus

A new oxytocic substance ex­hibiting properties different fromthose of any of the hitherto knownoxytocic peptides has been iso­lated from ox hypothalamus [Bio­chim. bioPhys. Acta, 160 (1968),286). It has similar thresholddoses when tested on rat uterus,guinea-pig ileum and hen rectalcaecum. The smooth-muscle sti­mulating action of the new sub­stance is not destroyed by incuba­tion with thioglycollate, nor anta­gonized by 1·44 x 10-8M atropinor 3·29 x 1O-7M dibenzyline. Theelution volume of the active mate­rial on Sephadex G-25 was similarto that of oxytocin at pH 2,9, butthe substance is separable fromoxytocin at pH 5·3.

Acetone-dried powders of oxhypothalamus were extracted at80°C in 10 vol of dilute acetic acid(PH 2·9). The cooled mixture wasshaken for 2 hr and spun at 1200 gfor 10 min at room temperature.The precipitate was washed withhalf the original volume of aceticacid and recentrifuged. The super­natants were combined and con­centrated in vacuo. The residuewas taken up in 0'05M ammoniumacetate buffer (PH 5'3) and spunat 1200 g for 10 min at roomtemperature. The supernatantswere subjected to gel filtration onSephadex G-25 columns (l'Ox 100cm) under the pressure of a hydro­static head of acetate at pH 5·3and 4°C. Fractions (2,0 ml) werecollected and pooled in the basisof absorbance at 280 mfJ. into anumber of peaks (AB, C & D).After concentration in vacuo, thepeak fractions were taken up inmodified Krebs solution and testedfor their biological activity againstsynthetic oxytocin on the isolated,isotonic uterus of the oestrus­induced virgin rats.

Quantitative analysis ofS-adenosylhomocysteinein liver

Estimation of S-adenosylhomo­cysteine in biological materials

NOTES & NEWS

has, so far, been hampered bytechnical difficulties, such as acidinstability and the lack of a quanti­tative method for the separationof adenosylmethionine and adeno­sylhomocysteine. These difficultieshave now been overcome in arecently developed procedure thatcombines isotope dilution withtwo consecutive separations by ion­exchange chromatography [Bio­chim. biophys. A eta, 158 (1968),461).

Freshly excised livers (30-50 g)from various vertabrates are de­proteinized by homogenization in1·5M perchloric acid (1: 4, wt/vol)and filtered. To the filtrate,labelled adenosylhomocysteine isadded and the mixture is chro­matographed through a Dowex-50(H+ form) column (resin bed:5 X 1 cm) previously equilibratedwith 0·5M H 2S04 , Elution iscarried out with 0'5M, 1M and3M H2S04 (0,5 ml of thiodiglycolper litre of eluant is used toprevent oxidation of adenosyl­homocysteine) until the absorbanceat 256 mfJ. is <0·05. From the3M acid eluate, adenosylmethio­nine and adenosylhomocysteine areprecipitated by the addition of20% phosphotungstic acid.The precipitate is dissolved inacetone-water (1: I, vol/vol) fol­lowed by extraction of the phos­photungstate with isoamyl etheraccording to the procedure ofSchlenk and Depalma [J. biol.Chem., 229 (1957), 1051). Fromthe aqueous solution, adenosyl­methionine is removed by de­composition with alkali [0·05MBa(OH). solution] and heating(100°C for 8 min). The solution isthen adjusted to pH 4 with 0'5MH2S04 and the BaS04 is discardedafter centrifugation. The super­natant is chromatographed on asmall column (3 X 0·3 cm) ofDowex-50 previously equilibratedwith 0·5M H2S04 to separate thedegradation products of adeno­sylmethionine (eluted with 1MH2S04) from adenosylhomocysteine(eluted with 3M H2S04), Thequantitative estimation of thethioether in the fractions (3Macid) is made on the basis ofthe molar absorbance (14200 at256 mfJ. in acid) and the radio­activity is determined with aPackard Tri-Carb liquid scintil­lation spectrometer using a scintil­lation solution containing 4 g of

2,5-diphenyloxazole in 500 ml oftoluene and 500 ml of ethanol.On the basis of the isotope dilutionformula, the initial amount ofadenosylhomocysteine in the tissuecan be evaluated with accuracy.

A new method for thedetermination of blood volume

A new and rapid method forthe determination of blood volumeusing indccyanine green dye (cardiogreen) has been developed. Theblood volume determinations aremade in patients by using radio­active iodinated albumin (Albumo­tope-RISA, Squibb) and/or chro­mium 51 (Chromotope, Squibb)tagged red blood cells. Indo­cyanine green dye (2'5, 5·0 or 10'Qmg) is injected through the samecentrally placed polyethylenecatheter (id 1·57 mm, od 2·08mm; length, 33 in.) as the isotopicindicator(s). Prior to the injectionof isotopes and indocyanine greendye, blood is withdrawn for cali­bration purposes. A separatethree-point calibration is plottedfor each indocyanine green dye­dilution curve. The blood collectedprior to the injection of the bolusin indicators likewise is used forbase counting of isotopic activity.The femoral artery is characterizedprecutaneously and serves as theblood sampling site. Constantwithdrawal of arterial bloodthrough a dichromatic densito­meter is accomplished by a Har­vard infusion-withdrawal pump.The analogue signal of the densito­meter system resulting from thewave fronts of changing opti­cal density at 805 mfJ. due toindocyanine green dye concen­trations is continuously recordedon one channel of a multichannelrecorder.

After the inscription of primarywave of the dye dilution curve,used for calculation of cardiacoutput, the withdrawal speed ofthe pump is changed from 15·3 to7·6 ml/min and the disappearanceof the indocyanine green dye fromcirculation is marked at the inter­val of 5 sec referenced to theinjection of dye as time zero. Asingle exponential function of thedecay slope is computed mathe­matically and extrapolated to givethe theoretical optical density dueto the dye at zero time. Theoptical density expressed as

33

J. SCIENT. IND. RES., VOL. 28. JANUARY 1969

millimetres deflection on the recordwas taken as variable and trans­cribed to a semilogarithmic plot.At 15, 25, 35, 45 min aft;.;r i'ljec­tion blood samples are collectedfor counting radioactivity due tothe isotopic indicators. The valuesof these samples are plotted inthe usual fashion and plasmavolume and red cell mass derived.

Besides the non-toxic nature ofthe dye used the other merits ofthis indocyanine green method arethe simplicity of the instrumentsrequired for plotting the changesin its concentration in blood; theprocess with which this dye isremoved from the circulatory sys­tem is also very rapid [Life Sci., 7(1968), 1001].

Pro~ress in leprosy research

Although Mycobacterittm laprae,the causative organism of leprosy,was identified in 1874, even longbefore the identification of manyother bacteria causing disease inhuman, the research on leprosyprogressed slowly, since M. lapraewas not cultured till 1960. TheNinth International Leprosy Con­gress, held at the Imperial College,London, during September 1968was dominated by the resultsobtained from fundamental andapplied studies based on experi­mental model infection in animals.Though only localized and limit­ed multiplication of M. lapraeresulted from mouse footpadinoculation of bacilli from man,this model infection was usedfor the determination of genera­tion time (12-15 days) to screendrugs for anti-leprosy activity andto demonstrate, for the first time,the emergence of drug resistancein patients on standard treatmentwith dapsone (diaminodiphenylsulphone).

Workers at the National Insti­tute of Medical Research, London,reported that more extensive andgeneralized infection can be ob­tained in mice made immunologi­cally incompetent by thymectomyfollowed by total body irradiation(900 r). The model infection ob­tained by both local and intra­venous inoculation of M. lapraereproduced a disease mimickinglepromatous leprosy seen in man,including more involvement andheavy infection of skin and nose.After a year or so, these nearly

34

infected mice develop intermediatetype, also seen in man. Similarchanges can be brought about inthymectomized irradiated micewith established lepromatous lep­rosy by donating back syngeneiclymphoid cells from normal mice,indicating the importance of im­munological capacity of the hostin determining the type of disease.

Dr Rees and his collaboratorsat the National Institute of Medi­cal Research, London, showedthat several of the cases of relapseduring treatment with dapsone orthiambutosine carry drug-resistantstrains of M. laprae. They haverecorded 18 dapsone-resistant aTJd5 thiambutosine-resistant strainsisolated from patients in Malaysia,India and Africa.

One of the important reportsat the congress was on the effec­tiveness of small doses of dapsone.Before the footpad technique be­came available, clinicians chosedoses of leprosy drug empirically.A trial in which patients weretreated with only 1 mg dapsone/day, compared with the previousstandard dose of 600 mg weekly,has yielded encouraging clinicaland bacteriological results [Natttre,Lond., 219 (1968), 1310].

Re~ional ResearchLaboratory, Jammu

The annual report of the Labora­tory for the year 1967 records theproduction, for the first time inIndia, on a commercial scale ofergot sclerotia of rye using thefungus strain [Claviceps pttrpttreaFr. (Tu!.)]. Work on large-scaleproduction of ergot is in progress.Of the several high alkaloid yield­ing strains, two (R-57 and R-56)producing mostly ergotamine andone (R-57) producing ergometrinehave been tested.

A simple method for the reco­very of xanthotoxine from theseeds of A mmi majtts has beendeveloped.

Cultivation of Datttra innoxiahas been carried out in order tohave the seeds as a source of thealkaloid, scopolamine (hyoscine).One lot of 50 kg of seeds yielded50 g of hyoscine hydrobromidebesides 9 litres of a fixed oil as abyproduct. A method has beendeveloped for inducing tetraploidsin D. innoxia and D. metel. Thetetraploids thus obtained have

high alkaloid contents. Plantswith as high as 0'50% alkaloidcontent have been produced againstthe normal alkaloid content of0'2-0'3%. Cultivation of Fago­pyrttm esculentum and F. tata­ricum (buck wheat), good sourcesof rutin has been successful inJammu. The leaves of F. tataricumgave a rutin yield of 5'7% (mois­ture-free basis).

The total alkaloids of Gloriosasuperba showed a superior bio­logical activity compared to purecolchicine. Experimental trials onthe cultivation of a superior strainof Ettcalyptus citriodora givingessential oil rich in citronellal havegiven encouraging results. Oilproduced from these plants is of ahigh quality in terms of its citro­nellal content and odour evaluation.A method has been developed forobtaining pure hydroxy-citronellalfrom citronella!.

The alkaloid usaramine isolatedfrom Crotalaria brevifolia was foundto possess marked hypotensiveproperty in anaesthetized dogs at adose level of 1·5 mg/kg. It alsoexhibited spasmolytic and anti­spasmatic activities in smoothmuscles of different animals. An­other alkaloid, integramine, iso­lated from the Crotalaria plantshowed hypotensive action. Thevolatile oil isolated from Tagetesminuta showed tranquillizing,hypotensive, anti-inflammatory,spasmolytic and bronchodilatoryactivities.

Methods for the extraction ofactive principles from senna(Cassia angustifolia) leaves andpods have been standardized. Aprocess has been worked out forrecovering the residual mentholfrom the spent oil of Menthaarvensis after the separation ofmenthol by chilling. A processfor the preparation of a stable.dewaxed and refined extract ofpyrethrins from the crude pyre­thrum oleoresin for use in theaerosols has been standardized.

Many of the plant materialsavailable locally have been sur­veyed for their suitability for thepreparation of paper and rayongrade pulps. Crude pine resinafter maleinization has given asatisfactory surface coating mate­ria!. A blend of the extracts ofpomegranate and polygonttm whenused for tanning hides gave leatherof satisfactory quality.

A process for converting the10cal1y available gypsum intosurgical grade plaster of paris andsurgical bandages of standardacceptable grade has been workedout. A laboratorv method torecover elemental slilphur of goodquality from sulphur ore depositsin the iadakh region has beendeveloped.

Pasteur Institute, Coonoor

Among the main achievementsof the Institute recorded in itsannual report for 1967 are thoserelating to the development ofSemple vaccine for the treatmentof rabies, development and im­provement of methods for thecultivation of influenza and otherrespiratory viruses and theirconcentration.

Extensive treatment trials haveestablished the superiority of 5%Semple vaccine over the 1%vaccine. The comparative efficaciesof ~-propiolactone (BPi) andphenol in inactivating 20% sheepbrain vaccine has been studied.It was found that in one-fourththe dose of phenol-inactivatedvaccine, the vaccine inactivatedwith BPi conferred the samedegree of protection. The antigenicvalues of sheep and suckling mousebrain vaccines inactivated withphenol and BPi have been com­pared. The antigenicity of suck­ling mouse brain vaccine in­activated with phenol was foundalmost the same as that of BPi­inactivated vaccine. The brainand salivary glands of guinea-pigswhich had survived on treatmentafter infection with street virushave been studied by the fluores­cent antibody technique. Thebrain and salivary gland of someof the guinea-pigs showed thepresence of rabies virus antigen.The finding lends support to theview that the fluorescent antibodytechnique reveals non-infectiveantigen material in treated ani­mals surviving an infection. Therewas no significant difference whenthe conjugates employing rhoda­mine B200 and fluorescein isothio­cyanate were used.

The occurrence of hydrophobiaamong persons bitten by ap­parently healthy dogs has beenexplained by a sub-clinical infec­tion in the animals with transientsalivary excretion of virus. The

NOTES & NEWS

possibility of reactivating the rabiesvirus in the tissues of a host bythe administration of a cortisonehas been examined. It was foundthat following the administrationof prednisolone, the dog excretedrabies virus in the saliva couldbe lyophilized.

Studies have been undertakento determine the presence of neutra­lizing antibodies in natural andexperimental rabies infection. Itwas found that neutralizing anti­body was present in only 17% ofsera from animals which developedrabies in spite of the treatment,compared to 59% in the sera oftreated animals which survived.This finding suggests that thechances of survival are betteramong animal containing neutra­lizing antibody than those with­out it.

The incubation period of therabies street virus was found tobe significantly prolonged in ani­mals which were treated with~-phenylserine post-infection.

The epidemiology and biologicalcharacteristics of 2 strains ofAsian influenza virus and 7 strainsof type B virus isolated earlierhave been studied. The propertiesstudied were (i) reaction to erythro­cytes from different species ofanimals, (ii) effect of ether, and(iii) effect of heat. Antigenic ana­lysis of strains revealed that whilethe Asian strain isolated during1967 resembled A2/Taiwan/64strain, the B strain was closelyrelated to the influenza B vari­ants.

Considerable progress has beenachieved towards the improvementof the medium used for the cultiva­tion of influenza virus in vitro.The effect of adding certain com­pounds, such as cephalin, glyco­cyamin, lecithin (egg) and 5-methylcreatinine sulphate to the mediumwas studied. The addition of eggalbumin in a concentration of2 mg/ml appeared to have themaximum beneficial effect on theculture.

Methods have been developedfor the preparation and mainte­nance of primary monkey renalmonolayer culture, primary rabbitmonolayer culture, primary humanamnion cel1 culture and BSc-lcell culture. By serial passage ofthroat swab specimens in primaryhuman amnion cell cultures onestrain each of adenovirus types 1

and 2 have been isolated. Boththese types are known to be latentin tonsils and lymphoid tissue ofpharynx. One strain of papin­f1uenza type I virus and two strainsof influenza A2 virus and influenzatype B virus have been isolated.

Three monovalent seed virusescontaining attenuated (Sabin) polio­myelitis virus strain, types I, 2and 3, have been prepared. Thesestrains were stored at -70°C andused for the preparation of livepoliomyelitis vaccine (Sabin). Theeffect of incorporating differentcompounds into nutritive agarmedium at pH 7·6 on the growthof V. cholerae has been studied.Potassium nitrate (0'5%) sup­pressed the growth of V. cholerae.Tartaric acid at 0'5% concentra­tion inhibited the growth of V.cholerae, S. typhi, Sh. boydii andAle. faecalis, while Esch. coli, B.proteus and Ps. aeruginosa grewwell in the medium. EDTA, sali­cylaldoxime, Ol,Ol-dipyridyl and8-hydroxy quinoline, at 0'3%concentration. have been found toinhibit the growth of all vibrios.The action of some dyes general1yused to render culture mediaselective was tested on V. cholerae.Crystal violet at a concentrationof 10 "g/ml caused completeinhibition of the growth of all thevibrios.

International Journal of SoilBiology and Biochemistry

To be published from early1969 by Pergamon Press Ltd,Oxford, this journal will act as amedium for papers on soil or­ganisms, their biochemical acti­vities and their influence on thesoil environment and plant growth.The journal will also publish papersdealing with biological transforma­tion of nitrogen and of other plantnutrients in soil; soil-borne phasesof plant parasites; the ecologicalcontrol of soil-borne pathogens;the influence of pesticides on soilorganisms; the biochemistry ofpesticide decomposition in soil;microbial aspects of soil pollution;the composition of soil populations;the biochemical activities of soilorganisms; and the interactions ofsoil organisms with one anotherand with plants. To be publishedquarterly, the annual subscriptionfor the journal will be £12 or$ 30.00.

35

J. SCIENT. IND. RES.• VOL. 28, JANUARY 1969

FORTHCOMING INTERNATIONAL SCIENTIFIC CONFERENCES, 1969

Organisatie Bureau Amsterdam,P.O. Box 7205, Amsterdam, theNetherlands.

• The Twentieth Meeting of theInternational Committee on Thermo­dynamic and ElectrochemicalSystems (ClTCE) will be heldat Strasbourg (France) during14-20 September 1969. The dis­cussions at the meeting will be on• Transport phenomena in electro­chemical systems' . The mainaspects to be covered include(1) theoretical and experimentalbasis of the phenomena; (2) massand charge transport in solution(in particular in diffusion layer);(3) mass transport in the poresof porous electrodes (particularlyin fuel cells); and (4) mass trans­port towards and through mem­branes (in particular in biologicalelectrochemical systems).

The last date for the submissionof forms by intending participantsis 15 April 1969. The forms canbe obtained from Dr H. Tannen­berger, Institut Battelle, 7 routede Drize, 1227 Carouge-Geneve,Switzerland.

appear in this new quarterly. Theannual subscription for the journalis £ 16.

Announcements

• The Sixth International Congressof Precast Concrete Industry willbe held in Amsterdam during17-23 May 1969. The congressis being organized by the Asso­ciation of Concrete ProductsManufacturers in Holland, theNetherlands number associationof the Bureau International duBeton Manufacture. About 1700delegates representing 50 countrieswill attend the congress.

The congress will have fiveworking sessions covering (i) qua­lity control; (ii) organization,mechanization and automation;(iii) structural lightweight con­crete; (iv) outstanding aspects ofthe manufacture and application ofprecast concrete; and (v) cons­truction of bridges with precast ele­ments. There is also an extensiveprogramme of technical study visits.

Further details can be hadfrom the Congress Organizer,

Weimar

BaselSheffield

Place

CortinaD'Ampezzo

Birmingham

Chicago

Warsaw

Montreal

MontrealLille

TorontoLiegeParisParis

BoulderMadrid

Paris

Great Britain

Dallas

Delft andThe Hague

Tucson

Conference

International Symposium on MicrowaveTheory and Techniques

International Colloquium on the OrganicChemistry of Phosphorus

3rd International Symposium on Yeats

International Conference on Arid Lands in aChanging World .

International Communications Conference7th International Food Congress and Exhi-bition

International Data Processing ConferenceInternational Colloquium on Classical andRelativistic Magnetohydrodynamics

4th International Federation of AutomaticControl Congress

8th Congress of the International Commissionfor Optics

5th International Congress on the Applicationof Mathematics in Engineering

7th International Shock Tube Symposium16th International Astrophysical Symposium7th International Aerosol CongressInternational Colloquium on Structure andProperties of Solid Surfaces

7th International Congress of Clinical Patho­logy

4th International Congress for PharmacologyInternational Conference on Atomic Absorp.tion Spectroscopy

8th International Conference on Medical andBiological Engineering

International Symposium on AnalyticalChemistry

25th International Union of Pure and AppliedChemistry Conference

Date

22-29 June

23-25 JuneJuneJune7-11 July

13-19 July

14-18 July14-18 July

20-25 July

21-25 July

July

Summer

5-8 May

19-24 May

2-6 June

3-13 June

9-11 June9-12 June

15-20 June16-20 June

16-21 June

Technological Forecasting

Elsevier Publishing Co Inc,New York, will start this newjournal from early 1969. The jour­nal will publish papers dealingdirectly with the methodology andpractice of technological forecast­ing as a planning tool, includingthe interrelationship of social, en­vironmental and physical factorsaffecting such forecasts.

Journal of Noncrystalline Solids

This new bimonthly journal hasbeen started by North-HollandPublishing Co, Amsterdam. Thejournal devotes itself to originalresearch papers and critical andauthoritative review articles onglasses and amorphous materials.The annual subscription for thejournal is $ 20.00.

New Periodicals fromPergamon Press Ltd

Geo Forum - This new journalwill publish papers on various as­pects of physical geography, eggeology, oceanography and mete­orology. The subscription ratesfor the journal are yet to beannounced.

Forma et Functio - This journalto be published quarterly willcarry papers dealing with morpho­logy, physiology, ecology andevolution in relation to func­tional biology. The annual sub­scription for the journal is £ 10.

Archives of Anthropology Inter­national Journal of ComparativeHuman Biology - This journal,which was started in 1866 andlapsed in 1943, is now being re­vived as a quarterly. It will dealwith palaeanthropology, physicalanthropology, population genetics,ethnology and social anthropology.The annual subscription for thejournal is £ 10.

Contribution to AtmosphericsPhysics - This new quarterly jour­nal reports the results of experi­mental and theoretical researchwork in all branches of meteoro­logy. Published in English, Frenchor German, all articles have sum­maries in other two languages.The annual subscription is £ 10.

Energy Conversion - Papers con­cerned with primary energy sour­ces, both direct and conversionprocess, and the problems associat­ed with regulation and control will

36

FISH & FISHERIESSupplement to the Wealth of India-Raw Materials: Vol. IV

This well-illustrated supplement provides information in an easy-to-grasp form on: (i) zoological

names of 376 fishes of economic value, found in Indian water, along with their English names; (ii) des­

cription and distribution of the fishes; (iii) coastal, deep sea and fresh water fisheries; (iv) ingenious

devices for catching and preserving fish; (v) fisheries in various States; (vi) manufacture of

fish oil and manure; (vii) analytical values of fish-foods and their byproducts; and (viii) marketing

practices and data concerning fish trade. An annotated bibliography of 220 references and an

exhaustive index are provided.

Pa~es iv+132 Demy 4to, 11 plates, including 2 coloured plates; 55 text figures

PRICE Rs 10.50, Sh 21 or $ 3.00

*

THE MILLIPEDE-THYROPYGUSCSIR Zoological Memoir No. 1

by

DR G. KRISHNAN

Director, Zoolo~ical Research Laboratory, Madras University

This well-illustrated memoir provides information on 10 species of Thyropygus. T. poseidon

Attems is describeu in detail, the account covering the following aspects: (i) external features;

(ii) integument; (iii) skeLeto-muscular system; (iv) alimentary canal; (v) blood-vascular system;

(vi) excretory organs; (vii) fat body; (viii) repugnatorial glands; (ix) nervous system; (x) sense

organs; (xi) neuro-secretory system; (xii) reprodllctive system; (xiii) larval development;

(xiv) water relations; (xv) habit and habitat; and (xvi) affinities. The memoir includes a selected

annotated bibliography and an cxh:lUstive index. Instructions for practical work are given,

which make the publication more useful for students.

Pages 84

PRICE Rs 12.00, Sh 24 or $ 3.50

Royal 8vo; 44 text fi~ures

Copies available from

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PUBLICATIONS & INFORMATION DIRECTORATE, CSIR

HILLSIDE ROAD, NEW DELHI 12

jSIR-JANUARY 1969 Al9

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A20 JSIR-jANUARY 1969

S. H. KELKAR & CO. (PRIVATE) LTD.Registered Office:

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eNS DRUGSA Symposium

Contains 32 papers covering diverse aspects of CNS drugs such as chemistry and

pharmacology of new drugs and known drugs, structure-activity relationships.

theories on the mechanism of action, development of tolerance and related

subjects. presented at the international symposium on CNS Drugs held at the

Regional Research Laboratory. Hyderabad. during January 24-30, 1966.

Pages xv+367; Royal 8vo Price Rs 33.00; Sh. 66 or $ 10.00

Copies available from

Sales" Distribution SectionPublications" Information Directorate, CSIR

Hillside Road, New Delhi 12

jSIR-jANUARY 1969 A21

~ELECTRONICS CORPORATIONOF INDIA LIMITEDPost Box No. 202, Hyderabad-l (A.P.)

The technology of electronics has made it possible toestablish communication with outer space through highlysophisticated precision instruments.

But an instrument is only as good as its components. Thosemanufactured by Electronics Corporation of India Ltd.have a built-in accuracy that confers high precision onelectronic instruments. The components produced includeresistors, capacitors and transistors, among others. Highstability carbon film resistors, high precision metalfilm resistors, multi-turn wire wound potentiometers, solidtantalum electrolytic capacitors, silicon zener diodesand germanium medium power transistors are used in avariety of electronic equipment having a wide range ofapplication-Scientific Research, Defence. Communications,Industrial Controls.

Among the important instruments manufactured are theGamma Ray Spectrometer, Geiger Counting System,Electronic Mullimeters and Oscilloscopes.

Components and instruments are all rigidlytested and re-tested to ensure the strictes:quality control. Constant checking IS anever-ending obsession.

00.,,_0 0 eo

A22 JSIR-JANUARY 1969

PUBLICATIONS & INFORMATION DIRECTORATE, CSIR

PUBLICATIONS

ENCYCLOPAEDIA

Wealth of India: Raw Materials

Vol. III (D to E)Vol. IV (F to G)Vol. V (H to K)Vol. VI (L to 111)Vol. VII (N-Pe)

Wealth of India: Industrial Products

Part III (0 to E)Part IV (I' to H)Part V (I to L)Part VI (:'II-Pi)

BOOKS & MONOGRAPHS

Rs 22.00 Sh 44 $ 6.60Rs 25.00 Sh 50 $ 7.50Rs 30.00 Sh 60 $ 9.00Rs 40.00 Sh 80 $ 12.00Rs 30.00 Sh 60 $ 9.00

Rs 25.00 Sh 50 $ 7.50Rs 25.00 Sh 50 $ 7.50Rs 30.00 Sh 60 $ 9.00Rs 28.00 Sh 56 $ 8.00

Aquatic Angiosperms - A Monograph by K. SUBRAMANYAM Rs 20.00 Sh 40 $ 6.00Coir: Its Extraction, Properties and Uses Rs 6.00 Sh 12 $ 175Flora of Delhi by J. K. MAHESHWARI Rs 28.00 Sh 56 $ 8.00Glossary of Indian Medicinal Plants by R. N. CHOPRA, S. L. NAVAR & Rs 8.00 Sh 16 $ 2.50

1. C. CHOPRAIndian Scientific and Technical Publications - A Bibliography Rs 25.00 Sh 50 $ 7.50Indian Essential Oils - A I<eview by A. K. MENON Rs 7.00 Sh 1+ $ 2.00Marsilea - A Monograph by K. M. GUPTA Rs 16.00 Sh 33 $ 5.00Kinetics of Electrode Processes and Null Points of Metals Rs 5.00 Sh 10 $ 1.50

by L. 1. ANTROPOVProblems relating to the Development of Internal Combustion Engine in Rs 12.00 Sh 24 $ 3.50

IndiaEssential Oils and Aromatic Chemicals Rs 1000 Sh 20 $ 3.00Cellulose Research: Vol. I Rs 6.00 Sh 12 $ 175Cellulose Research: Vol. II Rs 12.00 Sh 24 $ 3.50Antibiotics - Their Production, Utilization and Mode of Action Rs 15.00 Sh 30 $ 4.50Chemical Process Design - A Symposium Rs 18.00 Sh 36 $ 6.00International Geophysical Year: Vol. I - Symposium Proceedings Rs 18.00 Sh 36 $ 6.00International Geophysical Year: Vol. II - Symposium Proceedings l<s 18.00 Sh 36 $ 6.00Plant Embryology - A Symposium Rs 20.00 Sh 40 $ 6.50Low Temperature Carbonization of Non-caking Coals and Lignites and Rs 35.00 Sh 70 $ 11.00

Briquetting of Coal Fines - A Symposium: Vols. 1 and II eachNucleic Acids Rs 20.00 Sh 40 $ 6.00Patented Inventions of CSIR (1940 to 1964) Rs 16.00 Sh 33 $ 5.00I<ecent Auvances in Polymers by H. F. MARK Rs 2.50 Sh 5 $ 0.75Drug Addiction: with Special Reference to India by R. N. CHOPRA & Rs 12.00 Sh 24 $ 3.50

I. C. CHOPRAInuian Scientific anu Technical Publications (A Bibliography, 1960-65) Rs 18.00 Sh 36 $ 6.00Illustrations to the Flora of Delhi by J. K. MAHESHWARI Rs 28.00 Sh 56 $ 800Fluidization and Related Processes - A Symposium Rs 24.00 Sh 48 $ 8.00f:ldian FOisil Pteridophytes: A Monograph by K. R. SURANGE Rs 23.00 Sh 46 $ 8.00CNS Drugs - A Symposium Rs 33.00 Sh 66 $ 10.00

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