CHLORINATION OF HAIR AND pH 379 Figure 2c. Blond hair, 30 cycles of chlorination at pH 10. The values of percent weight loss with chlorination of blond hair are given in Table II. The effect of pH and cycles are again evident. Differences between the pH 2 and 7 values are not significant at any of the cycles. At 20 and higher cycles, the weight loss at pH 2 is significantly greater than that at pH 10. At 30 cycles, the difference between the pH 7 and 10 values is also statistically significant. Chlorination in acidic media gave the most rapid change in weight with cycles, the weight loss being significant between each pair of cycles. The samples chlorinated in neutral solutions show a more Table II Effect of pH and Cycles of Chlorination on the Weight Loss of Blond Hair Cycles pH % Wt. loss s* n** 10 10 0.7 0.23 5 7 0.7 0.45 5 2 1.0 0.42 6 20 10 0.6 0.11 5 7 1.6 0.60 5 2 2.6 0.49 6 30 10 1.0 0.32 5 7 3.5 1.10 5 2 4.3 0.85 6 * s = standard deviation. ** n = number of observations.

380 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS ß /,...__- ß .• -q . ,.• • . _. . • _ . Figure 3a. Brown hair, 15 cycles of chlorination at pH 7. ,•. ..• 3, -ø •, ...• .. • . "3• 'i"• ß i' [. ß . Figure 3b. Blond hair, 30 cycles of chlorination at pH 7.