ZINC OXIDE IN FACE POWDER 21 qualities. Its fungistatic action has been utilized by the paint and tex- tile industries as well as by the cos- metic industry. Zinc oxide is sooth- ing to the skin. On the hardness scale it lies between chalk and titanium &oxide (6). ('HEMICAL ('HARACTERISTiCS Chemically, zinc oxide is amph, -- teric, forming salts with both acids and alkalies. A water slurry of U.S.P. grade zinc oxide has a pH about 7.3 which classifies :t as a mildly alkaline material. Although there is considerable controvers) re- garding the effect of pH upon skin health, it would seem that a mildly alkaline material to neutralize acid exudations would be beneficial• Certainly some such neutralizatiot action must account for the deo& i' izing qualities long associated with zinc oxide in cosmetic usage. Zinc oxide is a highly water in- soluble solid even in its finely divided state only .00,5 grain dis- solves in a liter of water at 25øC. Chemical impurities are kept at a minimum in the U.S.P. grade. The U.S. Pharmacopoeia specifies rela- tiveiv low amounts of impurities in U.S.P. zinc oxide and our product is designed to be appreciably lower than these limits. PHYSICAL STATE In addition to the foregoing it is probably the finely divided state of zinc oxide that makes it the out- standing face powder ingredient. Zinc oxide is an air-born product. Its particles are formed separately and stay separated throughout their processing. It is a dry process-- there is no cementation of particles together on drying as in the case of wet precipitated pigments. Dry milling can never quite bring pre- cipitated pigments to as fine a de- gree of air dispersion as a pigment ,•hich has never been. wetted and dried during the course of its manu- facture. Zinc oxide and other fume products possess characteristics in the dry state which no wet-processed pigmen,• attain. It is this quality of air dispersion that probably accounts for the greater ease of blending and tinting of zinc oxide. REFERENCES (1) R. \V. Wood: "Physical Optics," pages 411, 512 (1934). (2) Stutz a,nd Pfund: Industrial & Engi- neering Chemistry, 1% 1, 51 (1927). (3) Stutz: Journal Franklin Institute 202, 89 (1926). (4) M. G. de Navarre: "Chemistry Manufacture of Cosmetics" (1941). (-3 Merck's Index, 5th Edition (1940). (6) Handbook of Chemistry & Physics, 28th Edition (1944). (7) Hegsted McKibbin and Drinker: "The Bi½logical, Hygienic and Medical Proper- ties ,,f Zinc and Zinc Compounds," Supp. 179 t• the Public Health Reports (1945).

EVALUATION OF EFFICACY AND SAFETY OF COSMETICS* By ALBERT F. GUITEP. AS Foster D. Snell, Inc., New York, N.Y. IT IS WITH considerable hesi- tation that I address this Society, because I am not a cosmetic chem- ist, and I realize full well that all of you know more about cosmetics than I do. My only excuse for accepting the kind invitation of the chairman of your Program Com- mittee is that I believe many of you may be more familiar with formu- lating cosmetics than with testing them. As one phase of our work as con- sultants, we are frequently called upon by outside firms to evaluate different products, many of which are cosmetics. The purpose of these tests is usually two-fold: first, to establish the safety of the product under conditions of use, and second, to determine .its effectiveness in accomplishing its intended objec- tive. Since it is difficult and often impossible to establish definite abso- lute standards, many of the tests, particularly the so-called perform- ance testsj are relative. In this case, comparative tests are usually run against several competitive products purchased on the open market. * Presented at the December 6, 1946, Meeting, New York City. 22 Safety tests are designed to deter- mine the safety of the product under normal' conditions of use by normal individuals. Thus, in determining the safety of a lipstick, for instance, we attempt .to establish whether or not it is apt to produce any irrita- tion when applied to the lips of a normal, average, healthy woman. We are not concerned with its pos- sible effects on a woman suffering from some particular disease, nor with any possible allergic manifes- tations. on hypersensitive individ- uals, nor with its effects on the gastro-intestinal tract if acciden tally swallowed by a child. The best method of determining the probable safety for use of most cos- metics and raw materials is the patch test. When working with new or unidentified materials, con- cerning the safety of which we can find nothing in the literature, we prefer to run some preliminary tests on rabbits, followed by a small number of humans working in our laboratory. This screening test is usually done on ten subjects and is for the purpose of discarding prod- ucts that may be strong primary irritants. Usually, these screening tests can