RESEARCH 1 Jc^H^v^^ *&\*&^&$ c »r>>v

GE's borazon (left) remains unaffected when placed on a resistance heater . But a small gem diamond (r ight) dis­appears when the temperature exceeds 1600° F. This

oxidation resistance, combined with its hardness, means borazon should make possible superior methods of mounting stones in industrial tools

As Hard as the Hardest A major scientific achievement, says GE of its n e w cubic boron nitr ide, which can scratch d iamond

οNLY DIAMONDS can scratch dia­monds—but that was yesterday, says General Electric. Today, diamonds can be scratched with a totally new material—cubic boron nitride (C&EN, Feb. 18, page 7 ) . Discoverer of bora­zon is Robert H . Wentorf, a member of the GE high pressure team that made synthetic diamonds in 1955.

Borazon, the new material, is quite similar to diamond in hardness, crystal­line structure, and density. But oxida­tion resistance is an important differ­ence. Diamond will burn up in air at 1600° F.; borazon can stand more than 3500° F. and still not decompose. "This oxidation resistance should make possible superior methods of mounting stones in industrial tools and also may allow bits and wheels to operate at higher speeds, performing their cutting and polishing jobs more quickly and efficiently," explains C. G. Suits, GE's research director.

"This is not a product," Suits says. "It is a major scientific achievement— the creation of a new material never observed in nature." Borazon is still a research tool and apt to be that for some time.

• Electrons Do It· What makes cubic boron nitride hard like diamond, not soft like graphite? Electrons do it, says GE. Graphite's carbon atoms are tied together in sheets that are weakly bound to one another. These sheets will slide past each other with ease. Diamond's carbons are also grouped in sheets, but unlike graphite's are tightly

bound to each other. T h e difference is a matter of electrons: Graphite has free electrons in its crystals; diamond, however, has used up its free electrons to form strong bonds between the sheets, and in turn, make a hard, not soft, material.

Graphite's crystal form is qui te similar to natural (hexagonal) boron

nitride. There is, however, an im­portant difference: Graphite conducts electricity well; hexagonal nitride does not. Reason: electrons again. Graph­ite has free electrons; ordinary nitride has none; hence, graphite will absorb light and appear black while the nitride will look white. (The latter is some­times called white graphite.)

Wentorf explains this phenomenon by saying that hexagonal boron nitride has used up its free electrons to bind its sheets together. That being the case, there was every reason to doubt cubic boron nitride could be made.

But one million pounds per square inch and temperatures above 3000° F .

Early samples of borazon are examined Percy Bridgman (left) a n d GE's Irving new material are GE's Herbert Strong

by two Nobel prize winners, Harvard's Langmuir ( r igh t ) . Demonstrating the (second from left) and R. H. Wentorf

2 8 C & E N FEB. 2 5, 1957

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The heteropolymolybdates comprise a unique family of giant mole­cules. Perhaps you can put them to work. To help you evaluate them, Climax has edited the vast and sometimes conflicting literature on these compounds into a new technical bulletin, "Properties of Heteropolymolybdates". It is a concise presentation that will serve as a guide to existing and potential industrial applications of these unusual chemicals.

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RESEARCH

brought boron and nitrogen together in t h e cubic combination. GE keeps exact process details a secret.

X-ray diffraction identified t h e cubic product . These studies showed boron a n d nitrogen packed together almost as closely as diamond's carbon atoms.

So far, GE has only m a d e a few grams of the new substance. Crystals have been white, yellow, red, brown, gray, or black. Although individual crystals are usually small—1/32 of an inch or so—they often grow together to make strong lumps about t h e size of a pencil eraser.

Tranquilizers & Tumors Tumors in mice can b e controlled

with reserpine and chlorprornazine. Tumors in untreated animals continued to grow at a normal rate so tha t at t h e end of five or six days, their average volume was about three times that of tumors in the treated mice.

Morris Belkin and Walter G. Hardy undertook the studies to see if reser-pine's effects on a lymphoid tumor (C&EN, Feb. 11, page 2 4 ) could b e duplicated in a solid tumor. Chlorpro-mazine was studied to see if the effects were a result of the prolonged state of depression reserpine induces .

In Feb. 8 Science, the Nat ional Can­cer Institute scientists conclude that t h e effects may be the result of t he d e ­pression. They feel these drugs a re another way to study the host-tumor relationship, particularly in conjunction with other tumor-necrotizing drugs.

Sr90 Levels Low So Far The average human has 0.12 micro-

microcuries of strontium-90 p e r gram of calcium, or 1/10,000 t h e presently accepted maximum permissible concen­tration. So say J. Laurence Kulp, Walter J. Eckelmann, and Arthur R. Schulert of Columbia's L a m o n t Geo­logical Observatory. This conclusion is based on 500 autopsy samples of h u ­man bones obtained from 17 stations in a world-wide network.

Averages for different continents a re surprisingly similar, indicating that Sr9 0

from megaton explosions is passing slowly (10% a year) from the strato­sphere, where it is more or less uni ­formly distributed with, respect to lati­tude , into the lower atmosphere, from which it is rapidly washed out . This Sr90 swamps the local concentrations the Nevada and Soviet test sites deposit in restricted latitudes. Distribution in the Northern Hemisphere remains higher than in the Southern Hemi­sphere because of the test sites, the

Columbia group says in F e b . 8 Science. Even with no more large tests, b y

1970 the average h u m a n bone i n the U. S. should contain 2 rnicrornicrocuries of Sr9° per gram of calcium; the world­wide average should b e about 1.3.

The most important problem lies with individual variation. Young chil­dren, for example, average three t o four times more Sr90 per gram of calcium than adults because their bones grow so rapidly. Some adul ts may have 10 times the average concentration.

T h e present results are part of a comprehensive study of the geochem­istry and biochemistry of Sr90. The Columbia group does no t consider i ts work complete. It investigated only one fission product, al thougli the most serious because of strontium's long half-life and bone-seeking properties. I t did n o t get into the genetic aspects of radioactivity. I t used a small sample.

New Antibiotic for TB Upjohn has discovered a new anti­

biotic it says is highly effective in de ­stroying tubercle bacilli. A complex of five antibiotics, it was isolated from Streptornyces spectabilis, a previously unidentified species. Studies now un­der way indicate the components may have unique structures for antibiotics. Its generic name is streptovaricin, t h e antibiotic trademark Dalac in .

T h e action of the antibiotic i s said to be unusual. In animal tests, it a p ­pears to immobilize the tubercle bacilli, rather than killing them. Upjohn r e ­searchers speculate the antibiotic might attenuate the bacilli. I n animal studies at Cornell , streptovaricin showed r e ­markable ability to enhance isoniazid's effect on the tubercle bacilli. The Cornell group says it "potentiates t h e action of isoniazid in mice t o a greater degree than has been seen with other of t h e conventionally used companion drugs to isoniazid, such as streptomycin or PAS."

In lab experiments a t Upjohn, strep­tovaricin was active against a wide variety of bacteria and also some fungi. It is about 10 times as ac t ive as s trepto­mycin and about 100 times as active a s PAS, but it is only half a s active a s isoniazid. Streptovaricin is not cross-resistant with streptomycin or any of the commonly used antibiotics,

Cornell used streptovaricin on 17 patients with advanced pulmonary t u ­berculosis. Results were no t dramatic. But its synergistic effect with s trepto­mycin makes the Cornell group still believe streptovaricin has promise i n TB therapy and so plans t o study t h e combined effect.

T h e antibiotic was discussed at t h e

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RESEARCH

16th Veterans Administration-Armed Forces Conference on Chemotherapy of Tuberculosis, held in St. Louis.

Prospecting Tool? Underground ore can b e located by

variations in oxygen isotope ratios in surrounding rock. The relationship has not been used yet in prospecting, but Caitech thinks "it could prove to be the basis for one of the most significant, contributions to ore prospecting in the past 50 years."

The greatest base metal deposits were formed when hot fluids, carrying ores with them, forced their way into carbonate rock formations such as lime­stone and dolomite. The intruding fluids permeated outward, heating the rock for considerable distance and changing it chemically. The affected areas, known as alteration halos, are usually 10 to 20 times larger than the ore deposits they surround.

For two years, geologist A. E. J. Engel and geochemists Samuel Epstein and Robert N. Clayton studied a Lead-ville limestone formation in Colorado. Specimens from the unaltered beds outside the halo showed no systematic variations in texture, concentration of elements, or oxygen isotope composi­tion. Specimens from the alteration halo showed no variations in texture or chemical composition, regardless of their closeness to the central ore de­posit. But the mass spectrometer showed that the ratio of O1 8 to O 1 6

varied directly with its distance from the ore deposit. The composition of the halo samples depended on the ex­tent to which they had been permeated and heated at the time of the original intrusion.

The oxygen isotope ratios provide a sort of "geochemical thermometer" ca­pable of taking temperatures that existed millions of years ago. I t should prove a valuable tool for studying origins of the earth's crust, Caitech says.

• A combination of mebrobamate and prednisolone is available from Merck, Sharp & Dohme Division for use in arthritis or similar conditions where muscle spasm, joint inflammation, anxi­ety, tension, and disability are contrib­uting factors. Mebrobamate has muscle-relaxant activity and predni­sone antiinflammatory activity.

> Research expend i tu res at New York University's college of engineering in­creased from $2,763,000 in 1955 t o $2,866,000 in 1956.

3 2 Ç & E N FEB. 2 5, ! 9 5 7

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