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

HAIR COLORING WITH OXIDATION DYE INTERMEDIATES 625 ! ß method that does not permit the simultaneous bleaching of melanin is hopelessly at a disadvantage when compared with the oxidative hair dyeing methods of today. In this experiment equivalent solutions were prepared except that the P.P.D. was eliminated. Natural dark brown hair was treated in these solutions in order to determine the amount of bleaching achieved. The color, as expected, became progressively lighter as the concentration of hydrogen peroxide was increased, with practically no bleaching occurring when the concentration was only 0.375%. It was found that the percentage yield of Bandrowski's base increased as the concentration of hydrogen peroxide was increased. However, under these conditions--at a concentration of 4.5% hydrogen peroxide, which is the most that can be used without substantial damage to the hair--the yield was only 8.86%. Heiduschka and Goldstein (23) also found that the yield of Bandrowski's base increased with increase in the concentration of hydrogen peroxide. It is interesting to note that, in the fur trade, the concentration of hydrogen peroxide is based upon the concentration of dye. The rule is that, in dyeing without a mordant, 15 ml of 3% hydrogen peroxide is used for each gram of dye. Since a 1.08% solution of P.P.D. was used in this experiment, this would mean that for each 100 ml of solution 16.2 ml of 3% hydrogen peroxide or a concentration of about 0.5% would be required. On the theory that one mole of hydrogen peroxide is required for each mole of P.P.D., as used by Heiduschka and Goldstein (23), the theoretical concentration of hydrogen peroxide would be 0.34%. Since the concentration of P.P.D. used in this experiment is approxi- mately the maximum amount used in dyeing hair, it is evident that when the concentration of hydrogen peroxide in the solution is 3% the amount used is almost nine times that required by theory and almost six times the amount that would be used in accordance with fur trade practice. The above facts suggest that a critical study on hair and heads, especially for dark shades, using hydrogen peroxide at concentrations less than 3% might be fruitful. In the next experiment the effect of pH, after the addition of the peroxide, on the yield of Bandrowski's base was determined. The re- suits are shown in Table XVII. All of the dyeings on natural white hair were black. Substantial bleaching of the natural dark brown hair was obtained in the pH range 9.3 to 10.0, with much less bleaching at pH 7.0 and 5.7. A maximum yield of Bandrowski's base of 6.52% was ob- tained at a pH of 9.8, with the yield decreasing slightly at higher pH values and substantially at lower pH's to a low of 0.59% at pH 5.7.