258 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS TABLE 2-A--EvVECT OV ADDITIVES ON T•E WAVING PROVERTIES OV MESO- AND D•-DMA IN BOT• CN AND AO PROCESSES Lotion Composition- , ,-- Process---- Experi- (NH4)2SS- Curl Level ment (NH4)2DMA NH4TGA* TGAt NH:, to (After 1 Shampoo) No. M M M pH CN AO 1 $.4 meso ... 9.28 60 100 2 0.4 meso 151i ... 9.28 85 110 3 0.4 dl 9.28 55 95 4 0.4 dl 61i '" 9.28 85 110 5 0.4 meso 0'.•)'5 9.12 90 6 Thioglycolate con•r •i ...... 100 ii6 * Ammonium thioglycolate. t Diammonium dithiodiglycolate. TABLE 2-B--EFFECT oF ADDITIVES ON WAVING PROPERTIES AND SULFHYDKYL LEVELS OF HAIR WAVED WITH DMA LOTIONS IN A CN PROCESS Experi- Composition. , SH Level,* NH4TGA NH.• iNH4)2DMALOtion to Curl Meq./G. ment No. M M pH Level Hair 0.50 9.30 65 0.27 0.45 6'i 9.2s 95 0,39 0.2 9.25 110 0'.'2'9 Thioglycolate control ... 100 0.22 * Measured just prior to chemical neutralization. the results obtained are given in Table 2-A. Again, for comparison, a standard thioglycolate lotion was used. The presence of a small amount (0.05 to 0.1M) of either thioglycolate or dithiodiglycolate in a 0.4M DMA solution boosts the wave level an average of 35 per cent. With these additives, a 0.4M DMA lotion is about equivalent to a thioglycolate lotion. This is true for both the meso- and the dl-DMA lotions. The results of the sulfhydryl analysis of the hair in these experiments do not indicate less attack by DMA than by thioglycolate (Table 2-B). However, it was shown that the distribution of the sulfhydryl groups was confined mainly to the periphery of the fiber when DMA alone was used, whereas thioglycolate-treated hair showed a more uniform distribution of sulfhydryl groups (see Figs. 1 and 2). Thus, it appears that for ad- equate waving to occur it is necessary to reduce more than just the periphery of the fiber in order to allow it to creep to a new configuration. C. Powdered FFaving Compositions Containing DM/1 In contrast to most other mercaptans, DMA has exceptionally high stability and low odor when kept as a dry solid or formulated in aqueous solutions. In Table 3 are given some stability data on typical powdered materials or solutions. The solutions are free of mercaptan odor before and after aging.

HAIR WAVING PROPERTIES OF 2,5-DIMERCAPTOADIPIC ACID 259 Figure 1.--Distribution of sulfhydryl groups in cross section of hair following exposure to DMA lotion but before chemical neutralization (stained with NQ reagent described in text) o Making use of these properties it is possible to formulate powdered DMA compositions with suitable booster additives which will give wave levels in a CN or AO process which are equivalent to thioglycolate waves. Table 4 lists some such compositions. D. 14Zaving End Papers Impregnated with Booster/ldditives for DM/1 Lo- tions Because of the odor and stability advantages of DMA, it is desirable to formulate aqueous lotions based on this mercaptan for commercial use. •..... .: . • ,..•.•...,:(.' • - : .. • •.• . ':'.: '•' •i ':?-,"- •' ........... • ":•' : r ß ß }g.' :: ...... -- :: • ß :... - . ..... : •- -., :: .... •, •,,,.,...........-'• :•, •,... .-•.. . ,. -- • . ..•? .• :, )•:,....•,.: (. • ..... .: . 5 . : •: .,.:. .:.. .• .- .,::.::.. , .... Figure 2.•Distdbufion of s•fhydryl groups in cross section of hair following exposure to thioglycolate lotion but before chemical neutralization (stained with NQ •agent de- scribed in text).