HAIR COLORING WITH OXIDATION DYE INTERMEDIATES Table XIV Effect of 'rime of Treatment on the Yield of Bandrowski's Base Time Average Yield of B.'s Base •' 5 minutes 1 04 623 15 minutes 1 30 minutes 3 45 minutes 5 1 hour 7 2 hours 12 4 hours 17 96 hours 57. 63 00 29 11 2 8 8 a Solutions were 0.1 Min P.P.D. and contained 3% H2Os. PH = 9.7 q- 0.2 T = 25 ø q- 2C. The numerical values are based on the averages of two determinations and are ex- pressed as % of the original P.P.D. Table XV Effect of Concentration of P.P.D. on the Yield of Bandrowski's Base Concentration of P.P.D. (M) Average Yield of B.'s Base a 0.2 5.12 0.1 5.93 O. 05 4.96 O. 025 4.59 a Solutions contained 3% HsOs--pH = 9.7 q- 0.2 T = 25 ø q- 2øC. The numerical values are based on the averages of two determinations after 45 min. of treatment and are expressed as per cent of the original P.P.D. statement appeared in a recent publication (25) that by using excess peroxide complete oxidation of hair dye intermediates to the final pig- ment form is achieved. Experiments were designed to simulate conditions used for dyeing hair in this country. The concentration of P.P.D. chosen was 0.10 M, which approximates the maximum amount used for dyeing hair, and the concentration of hydrogen peroxide was 3%. The pH of the solution was adjusted with ammonium hydroxide to 9.7 + 0.2 after the addition of the peroxide. The solution was made up to a final volume of 100 ml with deionized water. After the stated time at 25 øC + 2 øC, the solu- tion was filtered through a Gooch crucible of medium porosity, the precipitate washed with 50 ml of deionized water and dried at 105 øC. It was determined that a correction factor of 0.0029 g should be added to the weight of the precipitate in order to correct for the solubility of Bandrowski's base in the solution and wash water. For each experiment one of the conditions given above was varied while the rest remained constant.

624 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table XVI Effect of Concentration of Hydrogen Peroxide on the Yield of Bandrowski's Base Concentration of Hydrogen Peroxide (%) Average Yield of B.'s Base a 4.5 8.86 3.0 5.93 1.5 4.88 O. 75 3.28 O. 375 2.26 Theory: 1 mole of para phenylenediamine plus 1 mole of hydrogen peroxide --0.34%. Fur dyeing: -- 0.49 %. a Solutions were 0.1 M in P.P.D. pH = 9.7 q- 0.2 T = 25 q- 2øC. The numerical values are based on the averages of two determinations after 45 min. of treatment and are expressed as % of the original P.P.D. Commercial products currently on the market have recommended dyeing times of from five to forty-five minutes. In Table XIV the re- suits are given for an experiment in which the dyeing time was varied from five minutes to ninety-six hours. Natural white hair was dyed in another portion of each solution. All of these samples were dyed black except the one that had been treated for only five minutes, which was brown. These results confirm the fact that, under the conditions used, the oxidation of P.P.D. is a slow reaction. After forty-five minutes, which is the maximum time usually recommended for dyeing hair, only slightly more than 5% of the P.P.D. had been converted to B androwski's base. Even after ninety-six hours less than 60•o conversion had been achieved. In the next experiment the concentration of P.P.D. was varied from 0.025 to 0.20 M, with all other conditions remaining constant. The re- suits, given in Table XV, indicate that the percentage yield of Bandrow- ski's base does not vary appreciably in the concentration range studied. Natural white hair was dyed, as in the previous experiment. All of the dyeings were black except the one at 0.025 M, which was brown. Heiduschka and Goldstein (23) found that, under the conditions used, the percentage yield increased with increase in concentration. Next, the concentration of hydrogen peroxide was varied from 0.375 to 4.5%, with all other conditions remaining constant. The results are shown in Table XVI. Natural white hair was dyed, as in the previous experiments, and all of the dyeings were black. It has long been known that, in addition to the oxidation of the inter- mediate, another function of the hydrogen peroxide is to bleach and soften the hair. In fact, Lange (13) states that each new hair dyeing