The Crosslinking of Animal Fibres : I3: 4 isoPropylidene 1: 25: 6Dianhydromannitol

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    The Cross-linking of Animal Fibres 1-3 : 4 - isoPropylidene 1 : 2-5 : 6-Dianhydromannitol

    C. W. CAPP and J. B. SPEAKMAN When animal fibres me treated with 3 : 4-iaopropylidene 1:: 2,- 5 : 6-.dianhydromannitol for 24]hr. at 6 0 " ~ .

    in acid solution, cross-linking is brought about by reaction with the carboxyl groups of salt-linkages. The reaction proceeds more slowly at temperatures below 60c., and degradation is severe at high temperatures because of attack on the disulphide bonds. Under optimum conditions at 60%. the extent of cross- linking is smal1,'giving only about 7% increase in the resistance of the fibres to extension in water at 22*2"c., but even this limited amount of cross-linking causes an apprecisble reduction in the milling shrinkage of flannel. As the scaliness of the fibres is unaltered, the reduced shrinkage must be referred to the modified elastic properties of the.fibres, in agreement with the results of experiments with other crom-linking agents.

    It is well known that epoxy compounds, such as ethylene oxide and propylene oxide, are capable of reaction with amines, alcohols, phenols, thiols, and carboxylic acids in the following manner-

    R'.NH2:+ CHI--CH-R* + R'.NH.CHeCH(OH).R* '0/

    '0 ' R'.(!OOH + CH2-CH-R2 -+ R'TOOCHgCH(OH)*R2 The main peptide chains of proteins carry side- chains of all these types, and the conditions under which they react with epoxy compounds, especially propylene oxide, have been investigated by F'raenkel-Conrat and his colleagues1 in the case of soluble proteins, e.g. egg albumin and 1-lacto- globulin. Neutral, acidic, alkaline, and urea solu- tions of the proteins were used, and the optimum conditions for combination with basic, acidic, phenolic, and thiol side-chains established. In the light of these results, it seemed probable that di-epoxy compounds would be capable of cross- linking the main peptide chains of animal fibres, and a pure specimen of 3:4-isopropylidene 1 :2-5 :A-dianhydromannitol-

    CHrCH-CH- CH-CH-CH, \O/ 6 \(/

    Y< CHs CHs

    was kindly provided by Professor W. N. Haworth for use in the following investigation*. As the amount of pure reagent (R 1) was very small, the preliminary experiments were carried out with a sample (R 2) of rather lower purity, obtained from another source, but the total quantity of reagent was so small that its action on animal fibres had to be examined exclusively by mechano-chemical methods4.


    A sample of non-medullated human hair was purified by extraction with alcohol and ether in a Soxhlet apparatus, followed by washing in distilled water, and 5-cm. lengths, taken from the intact root ends, were then attached to light glass hooks by means of dental cement. After the fibres had been calibrated by determining their load-xten- ion curves up to 30% extension in distilled water


    Since the completion of this work in 194@ It has been reported* that Schlack has attempted to cross-link wool with dl-epoxy com- pounds.

    a t 22*2"c., they were treated with isopropylidene dianhydromannitol (R 2) for 24 hr. a t the desired temperature and pH. In each case, two calibrated fibres and two unmounted fibres were treated in 6 C.C. of a solution made up by mixing 0.25 C.C. of R 2 with 2.76 C.C. of water and 3-00 C.C. of double- strength buffer solution. Owing to the limited amount of R 2 available, the initial pH values of the reagents were not measfired, the values given in sub- sequent tables being those of the double-strength buffers diluted with equal volumes of water. It should, however, be mentioned that the final pH values of the solutions, although measured rather inaccurately because only 6 c.5. of solution was availablefor use with the glass electrode in each case, were close to the nominal values. Phosphate buffers were used for pH 4.63-7-96, and potassium ohloride-boric acid-sodium hydroxide buffers for pH 8-00 and 9.20.

    After treatment, the calibrated fibres were washed in running water for 20 hr. before redetermining their load-extension curves in distilled water a t 22.2"0., and the change in resistance to extension (30%) was then calculated. The unmounted fibres were used for supercontraction measurements. After each fibre had been mounted in a stainless steel setting frame4, its length wae measured with a travelling microscope. The fibre was then slackened, boiled in a 6% solution of sodium metabisulphite for 1 hr., rinsed, dried, drawn taut, and remeasured. In all cases the change in length was expressed as a percentage of the original length.

    For reference purposes similar data were obtained for fibres which had been treated with double-strength buffer solutions diluted with an equal volume of water only. The results of both sets of experiments are given in Table I, each value being the mean of two closely agreeing observations on different fibres.

    The change in resistance to extension of the ruagent-treated fibres is shown as B function of the temperature of treatment in Fig. 1. Maximum strengthening is realised a t about 5O0c., and since fibres treated a t this temperature show little or no supercontraction in a boiling solution of sodium bisulphite, it seems probable that strengthening is due to cross-linking of the main peptide chains. With rise of temperature above 500., however, the fibres are weakened progressively, to an extent which also increases with rise of pH. As the disulplude bonds of animal fibres are known to be


    Temperature of

    Treatment ("C.) 25.0



    TABLE I Change in Itesistance

    to Extension (yo) Reagent- Buffer- treated treated Fibres Fibres - 2.5 - 2.5 - 2.7 - 1.5 - 2.8 - 3.2

    0.3 - 1.5 0.5 - 2.0 2.1 - 1.3 5.3 0.9 4.a 1.1 4 .3 1.2 3.0 1.4 3.4 0.3 1.3 - 0.3

    - 0.9 - 0.8 0.7 - 0.7

    - 3.7 - 3.4 - 8.7 - 2.7 - 12.1 - 3.0 - 24.1 - 4.7

    - 51.7 - 25.8 - 77.4 - 31.8

    - 45.4 - 2 2 4

    Supercon traction (%)

    Reagent- Buffer- treated treated Fibres Fibres

    2 4 7 20.8 22.4 20.8 23.7 23.7

    6.0 20.9 2.9 19.9 1.7 14.0 0.0 18.6

    - 0.3 20.1

    2.4 23.5 - 0.2 1 7 4

    1.3 20.0

    1.5 25.5 4.2 20.9 1.4 24.0

    7.1 15.7 2.8 3.2 5.9 0.2

    0.1 28.2

    0.a 22.3

    1.0 21.6

    3.2 20.6

    10 30 40 50 60 70 80 90 100 Temperature of Treatment. ' C .

    0 pH 4.53 X pH 5.93 + pH 6.94

    FIQ. 1

    attacked by water a t temperatures above about 55'12.5, it seems probable that the weakening brought about by the di-epoxy compound is due to reaction with the products of hydrolysis.

    Some support for this view is provided by the failure of stretched fibres to acquire a permanent set when immersed in a solution of the reagent (R 2), in the usual concentration, for 24 hr. a t pH 4-53 and 50'12. After treatment, the stretched fibres were washed in distilled water and then released in boiling water. Data illustrating the rate of contraction of the fibres are given in Table 11, with corresponding data for fibres treated under similar conditions with the pH 4-53 buffer alone.

    The failure of the reagent-treated fibres to acquire a set permanent to boiling water, in spite of the cross-linking which has been shown to occur under the above conditions, is not surprising if the strained disulphide bonds of stretched fibres are

    TABLE I1 Percentage Extension after Release In Boiling

    0 2 15 30 00min. Buffer alone ... 38.7 1.7 - 1.3 - 2.0 - 1 2

    46.8 6.6 0.3 - 0.1 - 2.0 Buffer + reagent 39.3 8 8 - 2.3 - 3.6 - 9.0

    4 3 7 8.7 - 2.0 - 4.7 - 7.7

    Treatment Water for-

    hydrolysed at 50"c. and react with the di-epoxy compound without forming cross-linkages to m y marked extent. Few cross-linkages are formed when reduced fibres are treated with the di-epoky compound, as is shown in a later section, and it seems likely, therefore, that the above explanation why fibres are severely damaged by the reagent a t high temperatures, as well &B why stretched fibres fail to acquire a permanent set in the reagent a t BO"o., is correct. It is, however, surprising that stretched fibres treated with the reagent a t B0"c. should supercontract when released in boiling water for 80 min., because unstretched fibres, treated under similar conditions, fail to contract in a boiling solution of sodium bisulphite. Some cross- linking does, however, occur when untreated fibres are boiled in sodium bisulphite solution, as is indicated by the fact that they supercontract only 30% compared with 60% for dmminated fibres. Cross-linking during boiling in sodium bisulphite solution wnnot occur with deamimted fibres, and the absence of supercontraction when fibres treated with the di-epoxy compound a t 6 0 C . are boiled in sodium bisulphite solution seems, therefore , t o be due to the stability conferred on the structure by the two types of linkage, viz. those formed by the di-epoxy compound and those formed by the bisulphite.

    Further evidence that the strengthening of fibres treated with the di-epoxy compound a t 60C. is due to cross-linking of the main peptide chains was obtained in the following manner- Calibrated fibres were treated with isopropylidene dianhydro- mannitol (R 1) a t 60'0. under the same conditions as before, and restretched in distilled water to determine the increase in resistance to extension. The fibres were then immersed in 0.1 N. hydro- chloric acid for 24 hr. a t 22.2"c., and restretched in the solution with which they had reached equilibrium. Should either the mid or basic side- chains of salt-linkages react with the di-epoxy compound to form cross-linkages, the reduction in the resistance to extension in 0.1 N. hydrochloric acid, referred to the original resistance to extension in distilled water, should be leas than that given by untreated fibres in the same solution. The results are given in Table I11 with corresponding data for fibres treated with the buffer solutions alone under identical conditions.

    TABLE I11 Temperature of Treatment 60'0.

    (1) , (W (Ul) (W (il) - ( iv) 4.40 7.8 - 16.1 0.1 - 303 16.2 6.67 7 7 - 1 6 3 - 0 3 - 30.1 14.8 0.74 7.0 - 101 0.0 - 29.7 10.0 7.81 6.3 - 2 2 4 1.9 - 28.2 6.6

    - 24.2 - 3 3 - 43.2 10.0 8.70 4.1



    fi all cases, the buffer-treated fibres show a greater fall in resistance to extension in 0.1 N. hydrochloric acid than the reagent-treated fibres, the difference being approximately the same a t pH 4.40 and 5.57 (column 6 of Table 111). The differences are shown as a function of pH in Fig. 2, and it is interesting that a minimum should be observed at pH 7.5, followed by a rapid rise in more alkaline media. It scema probable that the form of the curve is to be explained in the following terms- the cross-linking of intact fibres proceeds best in acid media, and diminishes with rise of pH until thiol groups are liberated by disulphide bond hydrolysis to take part in new cross-linking reactions. Although only a limited number of such cross-linkages can be formed, as shown in a later section, they prevent the severe swelling and weakening which buffer-treated fibres undergo in the acid medium.

    Since the fall in resistance to extension of fibres treated with the di-epoxy compound at pH 4.40 and 5.57 is only about half that of corresponding huffer-treated fibres in 0.1 N . hydrochloric acid, it is obvious that either the acid or the basic side- chains of the salt-linkages which are normally broken by acid must have taken part in the cross- linking reaction responsible for the increased resistance to extension of the reagent-treated fibres. In order to discover whether acid or basic side-chains are involved, further experiments were carried out with deaminated fibres.


    After calibration, pairs of fibres were introduced into a 2-02. bottle containing 8.690 g. sodium nitrite dissolved in 34 C.C. water. Glacial acetic :tcid (7.2 c.c.) was then added, and the bottle closed with II stopper provided with a Bunsen valve. Deamination was allowed to proceed for 24 hr. a t 2 2 . 2 " ~ . The reagent was then renewed, and after a further 24 hr. the fibres were removed and washed overnight in running water. Their load-xtension curves were then redetermined in distilled water a t 22 .2"~ . In order to discover the extent of deamina- tion, the fibres were next immersed in 0.1 N. hydro- chloric acid for 24 hr. before determining their load-extension curves in the acid at 22.2%. Unlike untreated fibres, fully deaminated fibres show almost the same resistance to extension in 0.1 N. hydrochloric acid as in distilled water, and i t is obvious from the data of Table IV that the fibres used in these experiments were almost completely deaminated. The fibres were then washed in running water overnight before treatment for 24 hr. a t pH 6.05 and 50%. with the di-epoxy compound


    (R 1) in the usual concentrirtion. After treat,ment,, the fibres were :gain washed in runriing water before redetermining thcir load-extension curves in distilled water a t 2 2 . 2 " ~ Values for the clrange in resistance to extension a t the various stagrs of treatment are given in Table I V , with corrrspond- ing data for buffer-treated fibres.

    1 Deaminated Bbrea in wtitt'r _.. ... ~ 2 b 7 - 23.5 Deaminated Rbrw i i t 0 . 1 N-HC'I ... - 27.7 - z'!.li Ueaniinatetl Rbrra. treated with

    reagent and bntfer, in wHtw ... -- 1 9 4 - 16.0 2 Dearninated Bbres In wntrr ... ... - 26.3 -. 29.2

    Deaininated Bbrrs in 0.1 N-H(!I ... - 24.3 - 30.4

    The increase in rcsistarice to extension of the deaminated fibres (6.3 and 6.Si%), after treatment with the reagent, is so similar to that of untreated fibres as to leave no doubt that the carhoxyl groups of salt-linkages play an important part in the cross- linking reaction which is responsible for the strengthening of intact fibres by the di-epoxy coni- pound in acid media at 5 0 " c . Further support for this conclusion is provided by the fact that when fibres were treated for 24 hr. a t 50%. with the di-epoxy compound in presence of a phthalate buffer a t pH 4-99, the increase in resistance to extension in water, due to the treatment, was only 0.30/,, compared with 7.8% for treatment in presence of a phosphate buffer a t the same pH. Instead of combining with the fibre, the reagent combined with the carboxyl groups of phthalic acid, giving D buff-coloured, crystalline precipitate. Finally, since isopropylidene dianhytlro- mannitol appeared to be capable of cross-linking the acid side-chains of hair, it seemed likely that, alkali-resistant alginates might be obtained by cross-linking alginic acid with di-epoxy compounds. This work will form the subject of a later paper, but, in support of the above experiments with hair, it may be stated that highly successful results have been obtained. On nll these grounds, therefore, it seems safe to conclude that the main cross-linking reaction which occurs when wool is treated with isopropy1idei:e dianhydromannitol in acid media a t 5 0 " c . is as follows- R'COOH + CHI--CH-CH--CH-CH--CHI + H0OC.R

    \()/ A A \o/ ;c(

    CH. CH3 4

    R ~ C ~ ) O . ~ H , ~ C H ( O I I ) C H - C H - C H , O O C I I

    CHs 'CH:,


    From the preceding examination of the action of isopropylidene dianhydromannitol on untreated fibres a t different temperatures and pH values it was deduced that degradation a t high temperatures is assisted by the combination of the reagent with the



    thiol groups liberated by disulphide bond hydro- lysis. In order to establish that combination with thiol groups can occur, the action of the di-epoxy compound on reduced fibres was investigated.

    Six calibrated and a few unmounted fibres were reduced by immersion in 20 C.C. of a 1.001 M. solution of potassium thioglycollate for 2 lir. a t 5O"c. The fibres were then washed in running water overnight. In order to assess the extcnt of reduction, two of the calibrated fibres were restretched in distilled water a t 22.2%. The others, and some of the unmounted fibres, were treated with either 6 C.C. of the usual solution of isopropylidene dianhydromannitol (R 2), buffered to pH 433, or with the buffer solution alone. Both treatments were carried out for 24 hr. at 50c., and the fibres were then washed in running water before redetermining the load-extension curves of the calibrated fibres in water, and the percentage supercontraction of the unmounted fibres in a boiling 5% solution of sodium bisulphite. The results are given in Table V. A further test of the ability of the di-epoxy compound to cross-link reduced fibres by reaction with thiol groups was obtained by attempting to set stretched, reduced films with the reagent. For this purpose, 5-cni. lengths of the reduced fibres were stretched 40%, and then immersed for 24 hr. a t 5 0 " ~ . in 10 C.C. of the abobe buffered solution of the di-epoxy com- pound. After the fibres had been washed in riinning water for 15 min., they were released in boiling water and the rate of contraction was determined. For reference purposes, reduced fibres were also set in the buffer solution alone, and then released in boiling water. The results are given in Table 1'1.

    TABLE V Change in Resiatnnce

    Trratlnent to Extension Su[~errontrnctlon ( "U) (Yo)

    Reduced - 5 3 0 - 5 1 3 202 2 7 4 Reduced + buffer itlone - 37 6 - 38 4 25 2 27 2 Rrdnced + rengent +

    bnffrr ... ... ... - 13.2 - 17.3 0.2 -0.9

    TAIILF: VI I'errentngc Exteiwion after Relrusc in

    Srtt,ing Mrdinm Iioiiing Water f o - 0 2 15 30 50 mln.

    Huffer ... .,. 38.0 18.0 15.0 1 5 4 13.2 39.8 13.9 10.5 9.6 4.8

    Reagent + buffcr 3R.7 31,s 3 2 4 30.7 31.7 30.7 31.1 30.8 31.8 32.6

    That cross-linking does occur when reduced fibres are treated with isopropylidene dianhydromannitol is shown by the failure of the treated fibres to supercontract in a boiling solution of sodium bisulphite (Table V), but the results do not prove that there is reaction with thiol groups as well as carboxyl groups. Since, however, stretched untreated fibres cannot be set with the di-epoxy compound (Table 11), whereas the reduced fibres take a high degree of permanent set, it is obvious that the thiol groups of the latter must be cross- linked by the reagent. Some set is imparted to the stretched, reduced fibres by the buffer solution alone, due to oxidation during treatment, and since oxidation is brought about accidentally by

    atmospheric oxygen, it is not surprising that the results for different fibres are in poor agreement. Although there is thus clear evidence that the thiol groups of reduced fibres are cross-linked by the di-epoxy compound, the extent of cross-1 inking must be small because the resistance to extension of buffer-treated fibres is greater than'that of fibres treated with a buffered solution of the reagent (Table V). The presence of the latter seems to inhibit oxidative cross-linking of the thiol groups, probably by reaction with them, though without &om-linking. I n other words, only one epoxy group in the molecule of isopropylidene dianhydro- mannitol reacts with the thiol groups in most cases. This deduction is, of course, in complete agreement with the ability of the di-epoxy compound to accentuate the degradation of wool by buffer solutions a t high temperatures.


    In previous papers, it has been shown that all- wool flannel can be made unshrinkable by means of cross-linking agents such as mercuric .acetate and benzoquinonea. Since a limited amount of cross- linking can be brought about by treating hair with isopropylidene dianhydromannitol a t 5O"c. in acid media, it is to be expected that the ability of flannel to shrink during milling will he reducctl by the same treatment. A flannel having the follow- ing construction was used to test this decluction-

    Warp ... 32.4s Yorkshire skeins: 31 miis ppr in Weft ... 36.9s Yorkshire skeins; 31 picks per in. Weave ... Plain Weight ... 4 4 6 02. per sq. yd.

    Three conditioned 2.5-g. patterns were wetted out, centrifuged, and then each immersed in 48 C.C. of u solution made up by mixing 2 C.C. of reagent with 22 C.C. of water and 24 C.C. of double-strength buffer solution. The pH values of the three solutions were 4.53, 5.00, and 5.93. After being treated for 24 hr. a t 50"c., the patterns were removed and washed overnight in running water. Each pattern was then milled by hand for 15 min. with a wetted- out untreated pattern. A 6% solution of soap was used as the milling agent, and the resiilting shrinkages are given in Table VII.

    TABLE \'I1 Trentmrn t Shrinkage i n Awn

    (%) None ... 47.1

    None ... 3B.2 Reagent at'pH 6.'Ob ... 2543 None ... 47.3 Reagent a t p H 5:93 ... 40.9

    Reagent at',H 4.'i3 . ._ 30.1

    Only a small degree of unshrinkability is imparted to the patterns, iu keeping with the fact that the extent of cross-linking is smell. It is, how- ever, Satisfactory that these experiments confirm the ability of cross-linking reagents to reduce the felting power of wool. Further, the reduction is obtained without altering the scaliness of the fibres. For scaliness measurements, purified Lincoln wool fibres were treated for 24 hr. a t 50"c. with a solu- tion of the di-epoxy compound in the usud con- centration a t pH 4.43. After the fibres had been

  • 408 NOTES Bug. I849

    washed and dried, their scaliness was determined in air and in 0.2% sodium oleate solution by means of the lepidonietix-7. The reciprocating surfaces were clothed with polyvinyl chloride film, and the results for treated and untreated fibres arc given in Table VIII.


    compounds is combined with cross-linking of basic side-chains with formaldehyde.

    The authors are indebted to Messrs. Imperial Chemical Industries Ltd., Dyestuffs Division, for their co-opcration and for gifts of chemicals. TEXTILE CHEMISTRY LABORATORY

    DEPARTMENT OF TEXTILE INDUSTRIES LEEDS UNIVERSITY Mean Maximum Standard Nature of Conditions Tension developed Error

    Fiiires of Test (a.) (K.) Ilntreatrd Air-drs 1.107 0.016 (Received on 28M January 1949) Treatoil Air-dry 1,148 0925 Untresteil I n map solution 1.848 0.078 References Trentcd In soap solution 1,901 n 084

    In the light Of this survey Of the Fraenkel-Conrat, J . Biol. C l w w ~ , 1944, 154, 227; Fraonkel-Conrat and Cooper, ibid., 1944, 154, 239.


    isopropylidene dirtnhydromannitol on animal fibres, further experiments have been undertaken with a

    Of varying chain It is hoped that improved cross-linking

    will be realised, but even if the hope is disappointed, interesting results should be obtained when cross-

    * Berr, Cspp, Haworth, Spoakman, and I.C.I. Ltd., B.P. AppIication 9779 (29th March 1946).

    a B ~ ~ , ~ 1472: this ~ ~ ~ ~ ~ l , 1948, 64, 148. 4 Speakman, J . Textile Inat., 1947, 38, T 102. 6 Speakrnnii and Cooper, i bd . , 1938, 27, T 191. a Rerr and Speakman, this JoU-l, 11)44, 60, 335. 7 Speakman, Chamherlain, and

    Of di-epoxy length.

    J . Tertilo Inat., linking of acid side-chains by means of di-epoxy 1945, 36, T 91.

    Notes Proceedings of the Council

    At a meeting of the Council, held at the Offices of the Society, 32-34 Piccadilly, Bradford, on 18th May 1949, the proceedings included the following itemv of general interest-

    Biological Stains Cornmiltee - An invitation having been received from the Puthological Society of Great Britain and Ireland to co-operate in the work of a committee to be set up to consider the 8tandartlimtion of biological stains, it was resolved to appoint Professor W. Bradley to serve as the Suciety'e representative on this Committee.

    Rirles of the Manchester Section were approved.

    G'riess Cerctenary - A suggestion had been received that the centenary in 1958 of the discovery of diuzo compounds by Johann Peter Griess should he celelwatetl by a series of lectures, and it was decided that tho matter be deferred for further consitlerntion.

    Xembership- Seven applications for member- ship were approved.

    Annual Meeting of Chairmen and Honorary Secretaries of Sections 1949

    This meeting was held at the Central Hotel, Glnsgow, on 26th March 1949, under the chairman- ship of Mr. H. Jennison (Honorary Treasurer of the Society). Suggested subjects for lectures in the 1949-50 session were considered, and other topics of interest to Sections, notably joint conferences with other societies and social functions, were discussed.

    Meetings of Council and Committees J ~ Y

    Council- 20th Finance- 20th Publications- 19th Coloiir Index Editorial Panel- 27th

    Twenty-second International Congress of Industrial Chemistry

    Barcelona, 23rdSOth October, 1949 The third post-war congress of this series is to bc

    held in Spain, and its work will be divided into 'twenty-five sections, among which the following are most likely to be of interest to readers of this Journal- 1- Analytical laboratory equipment 2- Factory installntion and mnnagement, automatic control 3- Water 4- Manuftletaring processes (mcchaniral phy&al, and physial-

    12- Intermedlaks, colouring mattera, photographic products, powders

    13- Fats, B O ~ ~ S , essences and perfumes 14- Paints, varnishes, pigmenta, writing materiala 15- Natural resins, rubber, artlllolal plaatic materials 10- Cellulose and paper 17- (u ) Natural aud artI&lcial textilea

    (b ) Bleacldng, dyelng, prlnting, and llnislliug 18- Tlnctorlal and tanning extracts; tanning, glue, and gelatin

    industry 23- Scieiitillc and technical organlsntlon of research and toachlng

    bibliography nnd patents

    ohemieni operatious of clicuiical industries)

    aud exploslves

    Manuscripts of papers and applications for admission should be addressed to the Secretariat of the Congress, Camara Oficial de la Industria, Ancha 11, Barcelona, Spain, and further details may be obtained from the Soci6t6 de Chimie Industrielle, 28 rue St.-Dominique, Paris VII, France. Participants can obtain substantial reductions on the French and Spanish railways.


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