RESEARCH
pounds as A1 2 0, A1C1, Al 2 S, and AlO. It appears probable from data we now have that under these conditions metals will display all oxidation states from zero to the normal maximum. Carbon, for example, forms compounds in which it not only has the n o r m a l +4 oxidation state but also those with + 1 , -f2, and -f-3. This generalization is less certain in t h e case of the transition metals because of the lack of d a t a on their compounds at high temperature i n t h e gas phase. With gaseous halides, factors which favor oxidation states lower than normal are: • High temperature. • Low pressure. • Reducing conditions. As an example, Searcy cited his work on the dissociation of A1C13. At 1500° K. and a p r e s s u r e of 1 atmosphere of chlorine t h e ratio of A1C13 to A1C1 is about 1015. If t h e temperature is raised to 3000° K., t h e ratio i s decreased to 5 X 10 3 . Mow, if the pressure is also reduced from 1 atmosphere to 1 0 - 6 atmosphere, t h e ratio becomes 5 X 10 _ e . Under tHese conditions A1C1 becomes the p r e d o m i n a n t species.
Decontaminating Sea Water Sodium orthosilicate proves effective in removing r a d i o activity from saline solutions 10f|A^ I « i NATIONAL
Mixtures of fission products with sea water poses a Water,' Sewage, potential danger, & Sanitation especially for any Chemistry nation that dep e n d s on the oceans for its food supply. Radioactive decontamination is difficult. Complicating t h e problem a r e large amounts of salts as well a s many m a r i n e organisms. O n e w a y to r e m o v e radioactivity from saline solutions is b y coagulation and sedimentation. From 8 5 % to 9 5 % of a mixture of fission products in sea water can be decontaminated b y various clays, phosphates, silicates, and iron salts, used either alone or in combination, said Minoru Honma a n d A. E . Greendale of t h e Naval Radiological Defense L a b o r a t o r y
before the Division of W a t e r , Sewage, a n d Sanitation Chemistry. I n laboratory studies, only a single-stage stirring process w a s needed to obtain this amount of removal. Sodium orthosilicate is the best single decontaminant, they find. It works best at a p H above 8. As a result of his laboratory evaluation, H o n m a believes that it should be possible to reduce radioactivity in highly saline solutions to safe levels. Even greater efficiency should be possible by using a multistage coagulation process rather than single-stage stirring. Not all radioisotopes are adsorbed by floes, however. Monovalent cations, such as cesium-137, or anionic contaminants, such as iodine-131, are removed only in relatively small or negligible amounts.
Soap Monolayers Form On Metals Freshly exposed surfaces chemisorb f a t t y acids fast a t active sites; monolayer e x change also r a p i d
m
Fresh surfaces are produced whenever friction causes metal wear. Cellulose Polar organic moleChemistry cules added to lubricants form lowfriction films on rubbing surfaces. In studying this chemisorption, two chemists from t h e University of T e n nessee have found through radio-tracers t h a t freshly prepared metal surfaces, which are very active, lose this activity rapidly in the presence of air. In the absence of air, the surface energy decays slowly. Hilton A. Smith and Tomlinson Fort machine metal samples, with both tool a n d piece immersed in inert solvent containing a long-chain fatty acid. T h e active atoms furnish energy for the m e t a l / a c i d reaction, forming a monolayer of adsorbed soap. Smith told the Division of Colloid Chemistry that the amount of soap adsorbed per unit area is the same for a number of metals. This value, h e added, agrees with theoretical calculations which assume the surfaces to b e completely smooth. Determinations
were made using both carbon-14 tracers a n d conventional chemical analysis. • Tracers S h o w M o n o l a y e r " E x c h a n g e . " A radioactive soap film is produced on a metal surface by exposure to tagged fatty acid. When removed to a solution of unlabeled acid, the monolayer shows decreasing radioactivity. This indicates desorption a n d an exchange with the fatty acid in solution, says Smith. T h e exchange rate falls off with time, in t h e same w a y that the surface activity decays. Radiochemical measurements of these metal ions included i n the studies check well with straight chemical analyses when monolayers a r e desorbed into fresh solvent, Smith states. These show that the r a t e of desorption for t h e metals increases in the order: silver < copper < aluminum. And desorption for the aluminum soap is so rapid that it's hard to get complete monolayers. Considering activity to b e uniform on fresh metal surfaces, soap molecules are formed unexpectedly fast. Evidently, Smith feels, t h e r e are areas of high activity which give above-average exchange rates. I n the case of aluminum, he estimates the exchange at fifty times the anticipated rate.
ACS
NATIONAL MEETING
Properdin vs. Cancer? Hodgkin's researchers find no e v i d e n c e that properdin combats leukemia a n d c a r cinoma
m
Tests b y the Hodgkin's Disease Research Laboratory show that Medicinal properdin offers no -.'Chemistry;; answer in treatment of cancerous tumors. And preliminary experiments now going on at the laboratory indicate t h a t human properdin, when injected into mice, does not deter development of leukemia transplanted into r o d e n t s . Arthur L. Levy, of t h e laboratory, a n d his colleagues gave this evidence to the Division of Medicinal Chemistry. Levy did say t h a t properdin m a y b e an important weapon against bacteria invading the body. Tests point out it is able to inactivate a variety of microorganisms and some viruses. H e says the possibility of a tie-in of Hodgkin's ACS
NATIONAL MEETING
SEPT.
2 3,
1957
C&EN
73
