878 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS oxidation cycle was used just before the determination. The purpose was to intensify the damage and thus allow a differentiation between samples which are difficult to resolve otherwise. The hair was treated with 0.2M ammonium thioglycolate (pH 9.6, 35øC) for 10 min at a 20:1 liquor ratio, followed by a brief rinse and treatment with 0.2M H•O2 (pH 3.4, 35øC) for 5 min. The hair was then rinsed free of peroxide with deionized water. Thin-layer chromatography was employed for separating the melanin oxidation products. The adsorbent layer was silica gel (Merck), having a thickness of 250 v. Plate size was 5 X 20 or 20 X 20 cm. In cases where the subsequent elution of components was to be performed, the thin-layer plates were freed of possible impurities by their immersion in spectral grade methanol [or at least 30 min. The plates were then ready for use without any prior activation. Sample application was usually made by streaking the aqueous solu- tions onto the plate with the aid of a Brinkmann streaking piper. Whenever limited quantities of sample were available, the samples were spotted onto the plates with microliter pipers. Development of the plates was performed in a rectangular chamber (11 X 11.5 X 4 in.) containing 300 ml of solvent, namely, ethanol:am- monia:water in the ratio of 80:4:16. Overnight equilibration of the solvent, in a closed tank, lined with solvent-soaked paper, was necessary before its usage. A solvent migration of 17 cm required development times of 3-3.5 hours at ambient temperature. After the plates were developed, they were dried for about 20 min at 105øC. The resolved components were located by exposing the plate to ultraviolet irradiation from a 4-watt lamp with a spectral density of 3600 fk.* The spots or bands were located by their fluorescence. Other methods of identification included the following spray re- agents, prepared according to Stahl's (22) procedure: (a) Bromocresol green (0.04%) in ethyl alcohol (b) AgNO:,-NH.•: equal parts of 0.1NAgNO:, and 5N NH• (C) 50% H2SO4 (d) Ninhydrin, 0.3% in ethanol.* * Ultra-Violet Products, Inc., San Gabriel, Calif. 91778. ? As supplied by Sigma Chemical Co., P.O. Box 14508, St. Louis, Mo. 63178.

HAIR BLEACHING 879 RESULTS AND DISCUSSION Preliminary 0 bservations Stabilized aqueous solutions of H202 undergo little decomposition at ambient temperatures even at high pH values. However, the in- troduction of a solid into a system brings about an increase in the decomposition rate which is roughly proportional to the surface area of the solid. An additional increment in the rate of decomposition is observed whenever the introduced solid undergoes chemical reaction with H202. Table I shows the rate differences obtained under such conditions. Table I Decomposition of Hydrogen Peroxide in the Presence and Absence of Hair a H202 Decomposition (%) Time of Reaction, No fibers rain present White hair Brown hair 5 0 10 0 20 0.3 30 0.5 60 0.9 90 1.4 O8 21 42 61 94 13 5 0.8 2.5 6.5 8.0 14.2 21.1 a Bath ratio, 33:1 Initial [H20•] = 35 gl-• pH 10.0 35 ø C. Initially, with the reaction confined to the surface and to the cuticular region of the fiber, the rate of the peroxide decmnposition is ahnost identical for both brown and white hair. This is not surprising in view of the similarity of the dimneter and of the che•nical cronposition of both smnples of hair. It is likely that the divergence in the de- composition rates observed in the later stages of the reaction is associated with the response of the piginent, the granules of which are located within the cortex of hair and therefore not so readily accessible to the peroxide. Bearing in mind the low inelanin content of the studied hair (,-•2%), these observations connote a much higher reactivity of melanin than that of keratin. Galculations based on the data of Table I show that the overall rate of peroxide decomposition in the presence of brown hair is 9.0 X 10 -2 •nM •nin -• g-•, while the corresponding value for white hair is 6.4 X 10 -2mM min -• g-•. If the difference in H202