silicate, to form t h e a l u m i n u m silicate gel. T h e g e l goes next t h r o u g h a nozzle a n d is blown to a p i t for disposal. • M a y b e H e a t Treat, Too. T h e chemists have also found t h a t heat t r e a t m e n t changes the n a t u r e of the gel. F o r example, heat g e n e r a t e d by the radiation alone is e n o u g h t o turn the gel into a claylike substance. Higher temperatures melt this clay; t h e melt, w h e n cooled, yields a material similar t o porcelain, a n d temperatures of more t h a n 1000° C. will create a glass from t h e original gel. So far, t h e chemists do n o t know w h e t h e r these materials will resist leaching of t h e radioactive elements by water. But at this time, t h e y d o not plan to incorporate the h e a t treatment into their process.
RESEARCH
Cancer Only a Symptom
General Electric chemists h o p e t h a t by imprisoning cesium-137 a n d strontium-90 in a gel of sodium silicate they can b e buried in t h e ground directly rather t h a n in costly steel burial vaults. Demonstrating the custardlike consistency of the gel is Donald W . Rhodes; the other samples have been h e a t e d to high temperatures
GE Gel M a y Hold Radioactive Waste Silicate gel offers hope of eliminating costly underground storage tanks for "hot" fission products SODIUM
SILICATE, workhorse chemical,
may provide an answer to safe, low-cost disposal of some radioactive wastes from nuclear fuel element reprocessing. Preliminary work b y General Electric chemists at Hanford, Wash., h a s shown that an aluminum silicate gel can be formed continuously from reprocessing liquors in a pipeline-type reactor. T h e gel captures—both b y occlusion and reaction—cesium-137 and strontium-90 (now stored in dilute solution in underground steel t a n k s ) . It can then be blown as a custardlike mass into a disposal pit for burial. This treatment is not without difficulties, however. Although t h e gel is firm when first formed, it deteriorates upon aging. And, it bleeds water as it stands around. T h e bled water contains some radioactive cesium or strontium, but 42
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13,
1958
how much h a s n o t yet been established. However, t h e GE chemists are encouraged. If this t e c h n i q u e is successful, t h e expensive storage tanks could go. Burying globs of gelled wastes would cost a b o u t half as much as t h e present tank system, they estimate. • How It's D o n e . Irradiated u r a nium fuel elements a r e first dissolved in nitric acid. T h e u r a n i u m a n d plutonium are separated, a n d most of t h e nitric acid is recovered. T h e remaining reprocessing liquors contain aluminum (from t h e fuel element cladd i n g ) , cesium-137, strontium-90, a n d other fission p r o d u c t s . At present, this is the standard recovery process. G E chemists propose to a d d t h e new step at this point. T h e liquors, slightly basic, are mixed in a pipe with sodium
" T h e r e is no such t h i n g a s a cancer cure," R o b e r t D . Coghill of National Institutes of Health told a research and scientific development conference of the Proprietary Association. H e feels that cancer, like fever, should b e considered symptomatic of a large n u m b e r of diseases. Some 100 to 500 diseases, "depending on who's counting," are known to result i n cancerous growth, says Coghill, d e p u t y chief for industrial research at t h e Cancer Chemotherapy National Service Center. H e maintains t h a t it w o u l d seem m o r e practical to go about controlling cancer b y curing the individual diseases which bring it on. This goal can b e attained piecemeal, h e believes. Early clinical results show that 5-fluorouracil (long u s e d in tests on laboratory tumors) seem t o b e controlling one uncommon t y p e of cancer. If long-term reports continue to be good, Coghill feels that this m a y open the door to other strictly chemotherapeutic techniques. Screening of compounds b y C C N S C represents t h e biggest single operation in its chemotherapy p r o g r a m . I t directs preliminary evaluation of some 30,000 to 4 0 , 0 0 0 compounds a year, says Coghill. About 10,000 of these are synthetics submitted b y industrial firms a n d research laboratories; t h e rest are various antibiotic beers. Tissue-culture screening is an important p a r t of this work, b u t "mouse screening" is t h e technique most generally used. T w o million mice a year
give their all to this phase of the chemotherapy effort. Screening costs h a v e n o w reached $6 million a year, Coghill explains. This amounts to about a quarter of the entire $ 2 5 million cancer chemotherapy program. Nearly half of this, $12 million, is in t h e form of grants for fundamental investigations a t universities and research institutes. Almost $6 million more goes to the pharmaceutical industry and so-called "fringe" industries for their scientific contributions. Some $700,000 helps train people in colleges and universities for work in the field. Finally, administration costs account for about $500,000.
Clathrates Cage Isomers Complex organic compounds selectively trap hard-to-separate isomers, later recovered in high purity FORGING AHEAD with a clathration process, Union Oil researchers are purifying isomers that resist separation by conventional techniques. As described at the A C S National Meeting in N e w York (C&EN, Sept. 2 3 , 1957, page 7 8 ) , t h e process was viewed mainly as an effective w a y of isolating p xylene and ethylbenzene. Although this m a y prove to b e one of t h e most important uses for this process, the m e t h o d has been found to have much broader application, William D. Schaeffer of Union Oil told the recent meeting of t h e American Association for t h e Advancement of Science. The clathrating agent, tetra (4methylpyridino) nickel dithiocyanate, can b e used to separate t h e p-isomer from mixtures of m a n y different disubstituted benzenes, h e says. These include isomers of chlorotoluene, dichlorobenzene, toluidine, nitrotoluene, ethyltoluene, diethylbenzene, and others. This clathrating agent preferentially picks u p t h e p-isomer regardless of t h e substituent groups. The key factors are t h e isomer's size and shape. In this separation technique, t h e solid clathrating agent is a d d e d to t h e mixture of liquid isomers. By a physical phenomenon (not chemical bondi n g ) , t h e p-isomer is selectively t r a p p e d inside t h e clathrating crystals. The crystals are then isolated a n d extracted to recover the isomer. A t t h e same time, t h e clathrate-former is regenerated and can b e used repeatedly.
Initially, research on tetra ( 4-methylpyridino) nickel dithiocyanate centered around its use in isolating substituted benzenes, says Schaeffer in a report coauthored with W. Smith Dorsey of Union Oil and Curtis G. Christian, now with Gaspar Color. Recent work shows t h a t it can also separate isomers of substituted naphthalenes and anthracenes. It is particularly effective in isolating !-methylnaphthalene from t h e 2-methyl isomer. • Different Forms. Tetra ( 4-methylpyridino) nickel dithiocyanate is not t h e only clathrate-former of this type, Schaeffer emphasizes. T h e chemical composition of the three main segments of the molecules (the metal atom, t h e pyridine derivative, a n d the anion) can b e varied to meet specific needs. Preferably, t h e metal component should be divalent. Divalent forms of such transition metals as nickel, cobalt, manganese, and iron are especially effective. T h e hybrid bonding possible with these elements, h e says, may play an important part in determining t h e ability of the complex to form clathrates. Also important is the nature of t h e pyridine derivative in the complex. If it's 4-methylpyridine, p-xylene is selectively clathrated from a mixture of xylenes and ethylbenzene. If it's 4 hydroxymethylpyridine, o-xylene is clathrated. On the other hand, a complex containing 3-ethyl-4-methylpyridine preferentially forms clathrates with m-xylene. In other words, b y selecting the right clathrate-former, t h e chemists can carry o u t exactly t h e separation required. T h e third variable is the anion. Those studied so far include thiocyanate, cyanate, nitrite, chloride, a n d formate. Generally, the most effective are polyatomic anions, such as thiocyanate. • Commercial Future. As yet, Union Oil has no immediate plans for building a commercial plant to separate aromatic isomers b y these clathrating agents. At its research center in Brea, Calif., however, its scientists are actively studying m a n y of these compounds. Much e n gineering and pilot plant work will have to be done before the process proves itself. Nevertheless, this clathrating technique appears to have definite economic and quality advantages over other methods of purifying hardto-separate isomers. Research might well be done on at (Continued
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COMMENT . . . Real progress [in human knowledge] will be made only if all branches of science move forward together in an unbroken front. I would venture to say that there has been no great advance that was not a synthesis of knowledge laboriously accumulated in many different disciplines—a cooperative fusion of many branches of knowledge. For science, like freedom, is indivisible, and freedom in science is just as essential as freedom in any other area of human endeavor. We have encouraged people to be what they will, to pursue any course that seemed good to them. The inherent variability of human nature will inevitably produce sufficient numbers of practitioners to keep each of our scientific pots at the boil. Should artificial barriers be interposed which cause any of those pots to grow cold, not only that particular discipline but all of science will be the loser. In this country, we have emphasized the application of science to the production of things for our material welfare. We have even been accused, from time to time, of confusing scientific achievement with the production of egg beaters and car-washing compounds. I cannot dismiss utilitarian goals as unworthy of scientific application. It is indeed the ubiquitous nature of our scientific effort which stands in contrast with science as practiced in other countries, and particularly in the Soviet Union. American science is not a weapon, its edge sharpened fox military aggression, but a plowshare tilling the peaceful fields of our normal lives. It has been well demonstrated that our capacity to produce in time of peace is our greatest weapon in time of emergency or war. Hence, strength in war, strength in peace, and strength in science become synonymous. CRAWFORD H. GREENEWALT, president of D u Pont, before Sigma Xi and Scientific Research Society of America at American Association for Advancement of Science, I n dianapolis, Dec. 27, 1957. JAN.
13,
1958
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