TOXICOLOGIC AND CLINICAL INVESTIGATIVE STUDIES 167 One phase of our continuing study is, of course, toxicity of dihydroxy- acetone. We have no evidence that even in high concentrations that this compound is a primary irritant or even a sensitizing agent to the skin. However, after continued local use, under skih microscopy we have ob- served some dryness and scaling of the colored skin. Clinically, this is not significant. The cases of contact dermatitis which we have collected from all over the country seem to be related to the vehicles used in com- mercial preparations. Next, in order, we have no information as to its local effect on the carbo- hydrate metabolism of the skin. This we are studying with histochemical preparations of the skin and with chemical determinations. What about the absorption of dihydroxyacetone? Recent studies we have done with Guest and Wittgenstein of the Children's Hospital Group, indicate that dihydroxyacetone may be found in the blood after local ap- plication may be associated at times with significant elevations of blood sugar. These studies are being reported elsewhere. From the study of animal toxicity where the dihydroxyacetone may be as much as 10 per cent of the diet, it is obvious that chronic toxicity changes are observed. These are reported elsewhere. At present, we are doing feeding experiments in man with 18 grams, three times a day, over periods of two to three weeks. We are also studying the effect of dihydroxyacetone in the development of cataracts in animals. So, it is obvious that our toxicologic data at present are completely incomplete. These studies both of initial, acute and chronic toxicologic data must be continued es- pecially in man, and we emphasize man, if dihydroxyacetone is to be a standard agent in modern cosmetic practice. So, you see, there is much to be done besides additional advertising campaigns. Even if the fad fades or is given just to children to color their dolls, we shall continue to study it to attempt to develop better color, to understand its absorption and its effect on local and systematic carbo- hydrate metabolism and its effect on various enzyme systems. REFERENCES (1) Goldman, Leon, Barkoff, Joel, Blaney, Donald, Nakai, Takashi, and Suskind, Raymond, •7. Invest. Dermatoi, 35, 161 (1960). (2) Wittgenstein, Eva, and Berry, Helen K., Science 132, 894 (1960). (2a) Wittgenstein, Eva, and Berry, Helen K., "Reaction of Dihydroxyacetone (DHA) with Human Skin Callus and Amino Compounds," in press. (3) Blau, Saul, Kanof, Norman, B., and Simonson, Louis, At.M. At. Atrch.' Dermatol., 82, 69 (1960). (4) Maibach, Howard I., and Kligman, Albert M., Ibid., 82, 73 (1960). (5) Goldman, Leon, Blaney, Donald, and Goldman, John, "Topical Therapy with Dihydroxy- acetone," in press. (6) Bandelin, Fred J., personal communication. (7) Goldman, Leon, At.M.d. Atrch. Dermatol., 75, 345 (1957). (8) Goldman, Leon, Wittgenstein, Eva, Blaney, Donald, Goldman, John, and Sawyer, Faye, "Studies of Some Physical Properties of the Dihydroxyaceton½ Color Complex," in press. (9) Dihydroxyacetone furnished by Wallerstein & Co.

EVAPORATION AND THE ODOR OUALITY OF PERFUMES By J. STEPHAN JELLINEK, PH.D.* Presented October 5, 1960, New York Chapter THE FUNCTION and the reason for existence of any perfume is to be smelled. A perfume is a thing of no importance or interest until and unless someone perceives it. Perception of a perfume is possible only after some evaporation has taken place: molecules of the perfume material must leave their point of origin and travel to the olfactory membrane of the nose in order to be perceived as an odor. Although in the past perfumers have not given it much active attention, evaporation is a key process in perfumery. Since perfumes are usually complex mixtures containing materials of widely different vapor pressures, it is also a complicated process. The object of our research is and has been to study the process of evapora- tion of perfumes in all its ramifications, in the hope and certainty that our findings will have not only theoretical, but also distinctly practical, in- terest to the perruiner. EVAPORATION OF PERFUME MATERIALS Let us first take a general look at evaporation. If you have a perfume in an open bottle and you warm the bottle, the odor will be intensified. This is perfectly logical and we are all familiar with it. There is, however, another change which is more significant and less obvious. The odor character also changes somewhat as the perfume is heated. A perfume has many different ingredients, and it would be ex- tremely unlikely that the rate of evaporation of the various odorants would be increased in the same proportion by a given rise in temperature. This means that the vapor concentration over the perfume is different at the new temperature than it was at room temperature. Since what we per- ceive is not the liquid perfume in the bottle, but the vapor over it, a change in vapor composition means a qualitative change in the perceived odor. Apart from temperature there are other factors that influence the rate of evaporation of odorants and hence both the intensity and the quality of the * Polak's Frutal Works, Inc., Middletown, N.Y. 168