JOURNAL OF THE SOCIETY .barely perceptible. This is called "the threshold of perception of odor" and is assigned a numerical value known as the pO value. If two test pieces of gauze are worn under both armpits of several sub- jects for the same length of time, one axilla with and the other without a deodorant, it is possible to evaluate the effectiveness of the deodorant by the difference in the pO values. These tests are open to subjective influence, and great care must be taken to conceal the identity of the test sample from the observer. Most deodorants that are not anti- perspirants depend for their effec-' riveness on the fact that they pre- vent bacterial decomposition of per- spiration. The objectionable odor is due almost entirely to metabolic products produced by bacterial de- composition, since fresh perspiration has practically no odor normally. This type of deodorant is tested for its bacteriostatic properties. Anti- perspirant preparations may be evaluated in vitro by measuring their capacity to precipitate protein. Several in vivo methods have been purposed for determining antiper- spirant effectiveness on human be- OF COSMETIC CHEMISTS ings by measuring the amount of perspiration transpired from a given area in a given length of time. We have not had much success with any of these methods and we find it extremely difficult to duplicate re- suits. Any test requiring a diagnosis or evaluation of a skin condition is run in conjunction with a dermatologist. In order to avoid subjective influ- ence, the products are given code numbers. Neither the subjects nor the examining physician have any knowledge of the identity of the products or of the code system. Such tests are used to evaluate the relative effectiveness of hand creams, lotions, soaps, etc., where the original condition of the skin is compared against its condition after the use of a product or products for a definite period of time. In cases of doubt, the results are submitted to a consulting mathematician for statis- tical evaluation. , I have attempted to give you some of the highlights of safety and performance tests which consultants are frequently called upon to make on cosmetic products. There are others not mentioned here.
MERCAPTANS IN COSMETICS* By EVE•tETT G. McDo•oucH, PH.D. l/ice-President, Evans Chemetics, Inc., Nbw York, N.Y. AT mRST glance the title of this paper strikes one as a paradox, because the word cosmetics connotes a pleasant-smelling preparation, while the unpleasant odor of mer- captans is proverbial. In fact, they have been described by such terms as evil, provoking, ferocious, revolting, unbearable, and nauseating. The odor of mercaptans is most persistent even in extreme dilution. Emil Fischer(I) commented on the fact that ethyl mercaptan can be de- tected by smell in amounts as small as 2 X 10 -•2 of one gram. Note that this is less than 1/200 of the smallest amount of sodium that can be detected with the spectroscope. The revolting odor of the defensive secretion of the skunk is due to butyl mercaptan(2). Them•lodorof•eces (3) and urine (4) after asparagus has been eaten is at least in part due to the presence of methyl mercaptan. Meaning literally seizing mer- cury-the name mercaptan is derived from the Latin mercurium captans, and it originated in the fact that mercaptans react very readily with mercuric oxide to form crystalline compounds. Although the first synthesis of a mercaptan was re- * Presented at the December 6, 1946, Meeting, New York City. ported as early as 1834 by Zeise(5), the mercaptans as a group of com- pounds have been so little explored that no standard nomenclature has been adopted for them. There are 'at least five systems of nomenclature for mercaptan compounds and the need for systematizing the nomen- clature was the subject of a recent article(6). Undoubtedly mercaptans have been used in the synthesis of many other compounds, but these uses have never been publicized. In general their presence is not desired. In the petroleum industry alone, millions of dollars have been spent on research for methods of removing' mercaptans from petroleum. Dur- ing the first world war, n-butyl mer- captan was under consideration as a camouflage gas and a small plant did produce some. The second world war brought forth two uses ß lauryl mercaptan as a modifier in the manufacture of Buna S synthetic rubber and dithiog/ycero/ as an antidote or protective agent against Lewisite gas. The name "Bal" for British Anti-Lewisite is commonly applied to this latter compound since it was developed by the British. This compound is finding peace-time use as an antidote for 27
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