TRACER CHEMISTRY 295 problem. The highly ionizing alpha particles make the air conducting so that these accumulated changes can leak off. Small sources can be placed inside analytical balances to accomplish the same thing (9). Beta ray gauges, employing Stron- tium øø, are being installed every day in paper mills, rubber factories, and steel mills to measure the weight and thickness of these materials on a continuous basis by a non- contacting method. This type of gauge makes use of the principle of absorption of beta radiation as a function of mass. By tagging sewage with radioiso.- topes it has been possible to explore the extent and course of pollution in our water systems. Labeled sodium has been used to test the enteric coatings of cap- sules. The cleaning abilities of various detergents have been studied by tagging soil (10). TRACERS FOR THE COSMETIC CHEMIST Thus far the literature on this side of the ledger is very small in- deed. I do believe, however, that the little that has been done points the way. The absorption by the skin of mustard gas and lewisite labeled with Sulfur a5 and Arsenic TM, respec- tively, has been studied (11). The tracer method reveals that lewisite is fixed in the epidermis with very small amounts in the dermis. It is also found in hair follicles and some blood vessels. Mustard gas is found fixed in the epidermis and dermis and has been shown to penetrate deeper than lewisite. The absorption of Thorium x in the skin has been studied by the autoradiographic technique to un- cover the route that Thorium x takes after being applied to the skin. This study will eventually attempt to relate the therapeutic effects noted with the radiation effects produced within the complex structure of the skin, (12). ' Cold cream has been labeled and found to penetrate only very slightly in skin. The cancer producing substance methylcholanthrene has been tagged with Carbon TM and found in the cancer produced by it. It is possible to label most of the 2000 ingredients used in cosmetics to study the absorption of these in skin. Radioactive strontium and cal- cium are available to tag these elements in depilatories which base their results on the action of the sulfides of these elements. To what extent does propylene glycol or glycerin function as a percutaneous vehicle? Why not tag these with radioactive carbon and find out? Sulfur a5 labeled thioglycolates can be made readily available to study the action of these on the hair. Does ammoniated mercury pene- trate the skin? A suitable radio- active twin, Mercury 2øa, can be used to resolve this question. The stability of emulsion may be evaluated in a fraction of the time

296 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS that it now requires by labeling one of the ingredients. A Geiger counter can detect the "settling out" of the internal phase long be- fore a deposit would become notice- able to the eye. Fingernail preparations may be labeled to determine their ability to withstand wear under various conditions. By the same token one may tag lipstick. It hardly seems necessary to expound on the interesting studies available here. Those who want to look into the possibilities of the new tracer tech- niques will find the Isotopes Divi- sion of the Atomic Energy Com- mission ready to co-operate and advise at all times. A special train- ing division has been set up at Oak Ridge where the researcher can ac- quire the necessary knowledge in one month's time. The cost of setting up a labora- tory, according to the Atomic Energy Commission, averages around $1640 for a one-room laboratory, $7500 for 2 rooms, and $12,900 for a 3-room laboratory. Safety procedures and standards have been formulated and a Na- tional Committee on Radiation Pro- tection makes recommendations from time to time. I do not want to minimize the potential hazards ß e involved in using radioelements, but it is a fact that the safety rec- ord established in the nuclear field is an enviable one. Perhaps a thorny problem has been shelved for lack of a suitable technique? I believe that tracers have much to offer cosmetic chem- ists and am strongly inclined to believe that your laboratories can benefit by reserving space for this new and powerful research tool. BIBLIOGRAPHY (1) Hcvcsey, G. V., and Zcchmcister, L., Bet., 53, 410 (1920). (2) Libby, W. F., Phys. Rev., 69, 671 (1946). (3) Allen, H., Jr., Libby, R., and Cassen, B., 2 t. CSn., EndocrinoL, 11,492 (1950). (4) Err, L. A., "Primary Polycythemia: Remissions Induced by Therapy with Radiophosphorus," Blood, 1,202 (1946). (5) Hahn, P. F., et al., "Direct Infiltration of Radioactive Isotopes as a Means of Delivering Ionizing Radiation to Dis- crete Tissues," 2 t. Lab. Clin. Med., 32, 1442 (1947). (6) Smith, B.C., and Quimby, E. H., "The Use of Radioactive Sodium as a Tracer in the Study of Peripheral Vascular Disease," Radiology, 45, 335 (1945). (7) "Isotopes, Catalog and Price List," Atomic Energy Commission. (8) Pinotti, D. L., Hull, D. E., and Mc- Laughlin, E. J., "Application of Radio- active Tracers to Improvement of Auto- motive Fuels, Lubricants and Engines," SAE •ournal, 57, No. 6, 52 (1949). (9) "Eliminating Static Electricity by Radioactivity," Atomics, 2, No. 3, 71 (1951). (10) Harris, Kemp, and Yanko, "Detection of Soil Removal in Metal Cleaning by the Radioactive Tracer Technique," •. Electrochem. Soc., 97, (1950). Axelrod, D. J., and Hamilton, J. G., Am. •. Path., 23, 389 (1947). Witten, V. H., Ross,, M. S., Oshry, v.., and Hyman, A. B., 'Studies of Thorium X Applied to Human Shin," 5 •. Investi- gative Dermatology, 17, No. 6, 311 (1931). (11) (12)