MERCAPTANS IN COSMETICS 31 of a beauty shop, and cold waving alone accounts for over 30% of the shop's income. As the total yearly income of the beauty shops of America is estimated to be one billion dollars, cold waving not only becomes the most significant source of income for the 300,000 beauty operators but also plays an impor- tant role in our national economic structure. All of this commercial revolution has happened since the spring of 1941. After the unfortunate death of an Atlanta matron who had just had a cold wave, the Federal Government effectively halted all cold waving by the seizure of the cold wave lotions. These, however, contained ammonium hydrogen sul- fide, which was the only chemical agent then used commercially to wave hair at low temperature in a short period of time. One large chain of beauty salons which had spent a small fortune in ventilating equipment to dispose of the toxic and malodorous hydrogen sulfide gas was the first to utilize commercially a cold wave lotion con- taining mercaptan as the successful displacement for the noxious sulfide lotions. Thus at one stroke the poison, bad odor, and cumbersome equipment associated with the use of the sulfide lotions were displaced by the mercaptan lotions which are superior in every respect. The cold wave product introduced by this group of salons was an earlier discovery made as a result of exten- sive research and development in our laboratory. The principle is that mercaptans, particularly in an alkaline medium, were effective waving agents and could be used for waving at low temperature. With- out going into the details of these experiments, some of the conclu- sions reached were as follows: The substituted mercaptans were not only more effective but also preferable because in the proper medium they gave less odor. The concentration of the mercaptan was less than 15% and preferably was in the range of 2% to 10%. In cold waving with mercaptans the range of pH is very important. Although below pH 7 cold perma- nent waving is possible, the time re- quired is very long. No critical difference in time is noted below pH 7. At this pH there is a break, for at this point the time to 'wave sharply decreases with even a slight increase in pH. The critical upper limit for pH is 10, because at this pH and above, the hair is seriously damaged before it can be waved satisfactorily. A particularly critical range of pH is from 9.2 to 9.5. Within this range the hair can be waved quickly without being damaged therefore, this range is to be preferred for com- mercial use especially in beauty shops. Although many alkaline com- pounds may be used, the bases hav- ing a dissociation constant less than 5 X 10 -3 give the best results. The volatile bases are particularly effective for example, ammonia and ethylamine are preferable to the non-volatile monoethanolamine.

32 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS and this, in turn, is preferred to the ß stronger alkalies such as sodium hydroxide. Waving with metcap- tan is remarkably kind to the hair. ß Despite recent publicity, waving with thioglycolic or other metcap- tans can be done with complete safety. As a matter of fact, it is a testimonial to cold waving with thioglycolic acid that only two ad- verse articles have been published, and both of these are open to con- siderable criticism. Answers have been made and are being made to these two articles elsewhere. It is sufficient to say here that statistics prove the safety of mercaptans in cosmetics. With both depilatories and cold waving there are tremendous expanding markets yet the insurance rates on both products have been constantly decreased. In conclusion, it should be pointed out that these two commercial uses of mercaptans in cosmetics will un- doubtedly serve not only to stimu- late interest in the use of them in other cosmetics but also--more important--to remove the barrier of prejudice against many other chemical substances which we in the cosmetic industry may have thought of no value because they of them- selves displeased our aesthetic senses. It was as a result of the two dis- coveries discussed here that research brought thioglycolic acid (and other mercaptans) from the status of laboratory curiosities to full scale commercial production. New uses for these products are now being evaluated and thus the cosmetic industry once again indirectly affects the well-being of other in- dustries. REFERENCES CITED 1. Fischer and Penzoldt, dnn., 239, 131 (1887). 2. Beckmann, Pharm. Zentra/halle, 37, 557 (1896). 3. Nencki and Sieber, Monatsh. 10, 526 (1889) Ber., 34, 201 (1901). 4. Nencki, Ber., 25, 512c (1892). 5. Zeise, dnn., 11, 1 (1834). 6. 'Ball and Haines, Chem. Eng. News, 24, 2765 (1946). 7. Koeune, Mfg. _Perf., Feb., 1937, 158. 8. Consumers Reports, No. 211 Aug., 1946.