388 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Determination of Toxic Properties of New Formulations For the smaller companies, this is generally done by well-established testing laboratories both on animals and human subjects. The larger companies maintain their own special laboratories for this purpose. As was pointed out by Wilmsmann (32), in dyeing growing hair diffu- sion of the color into the fiber is hindered by the low temperature of dye- ing, the high viscosity of the dye solution, and the restriction of move- ment of the dye in solution caused by the fact that it is applied by brush- ing rather than by immersion. Penetration of the dye into the hair fiber can be increased by swelling the fiber, the use of carriers, the adaption of the electrical potential of the fiber to the state of the electrical charge of the dye ions, and by decreasing the size of the dye molecule. INDOPHENOL AND INDAMINE DYES The plan of the research reported in this paper was to prepare dyes having as small a molecular size as possible and test them for application as semipermanent hair colors. The indophenols and indamines (some- times called indoanilines), which are basically two substituted benzene rings connected by a nitrogen atom, are among the smallest dye mole- cules known. Because of their poor stability they have little value in the textile field except as intermediate products in the manufacturing of sul- fur colors (33). Most of the recent attention to the indophenols and indamines has been directed towards their use in color photography (34). While the simple indophenols and indamines are generally of insufficient stability to be practical for use as dyes, it has been shown (35) that the introduction of halogen or alkyl groups yields dyes of enhanced stability. In our research, many substituted indophenols and indamines were prepared and screened for their substantivity for hair, light fastness, and shelf life. Substantial retention of color by the hair, a fastness to light of 10 hours, and stability of the dye solution for 1000 hours at 50øC in a sealed bottle were selected as minimum standards. Since it is likely that most of these prepared indophenols and indamines would fail to pass one or all three of these tests, it was decided to use only these tests in our evaluation and designate those dyes that pass for further consideration. Since all of the indophenols and indamines that were prepared belong to the class known as solvent-soluble dyes, it was decided to apply these three tests to a substantial number of the solvent-soluble dyes listed in the Color Index (33), in order to determine the type of result that could be expected. This was done using 93 regular solvent-soluble colors. Of

COLORING WITH SEMIPERMANENT DYES 389 these, 64 (70%) failed to pass the substantivity test and were therefore eliminated. This left 29 dyes that were given the light fastness and age- ing tests. Of these, 12 (about 41%) failed to pass the light fastness and 6 (about 21%) failed to pass the ageing test. In other words, only 13% of the regular solvent-soluble dyes evaluated passed these tests. Preparation of Indophenols and Indamines Indophenols are formed by the oxidation of equimolar quantities of a p-aminophenol and a phenol. Indamines are formed by the oxidation of equimolar quantities of a p-phenylenediamine and a phenylamine. These reactions are shown as follows (36): HO•NH2 + •OH O, (CHa),,N•NH2 + •NH• Indophenol (CHa)2N•N==•NH Indamine Although the reactions have been reported to be affected by various oxidizing agents (37), the sodium hypochlorite method has been used for our preparations. A typical formula for the preparation of an indamine is the following: 6.8 g (0.05M) of p-aminodimethylaniline is dissolved in 350 ml of water and another solution is made by dissolving 5.4 g (0.05M) of m-phenylenediamine and 1.5 g of sodium hydroxide in 150 ml of water. The two solutions are mixed, then cooled to 0øG by adding ice. Next, 115 ml of sodium hypochlorite (5%) solution are added slowly, with stirring, keeping the temperature below 5øG during the ad- dition. The mixture is stirred for 30 min after the last addition without further cooling, then filtered and dried. The yield was 82%. Isopropyl alcohol was used, in some of our preparations, to replace some of the water, with the amount used depending on the solubility of the intermediates. The final pH of the dye preparation solution was about 9.9. After the solution had been filtered, the flitrate was acidified with acetic acid to a pH of 6.0 and any precipitate formed was removed by filtration. In some preparations, as in the one given above for indamine, a substantial yield of dye was obtained upon filtration of the basic solu- tion, while with other intermediates most or all of the dye was obtained upon filtration of the acid solution. It is well known that the oxidation of p-phenylenediamine with hy- drogen peroxide in alkaline solution yields Bandrowski's base which has