ABSORPTION OF CHEMICALS ON SKIN 147 200- lOO ß ß ß ß ß ß [] ß A B C D E F G H I K Figure 4. Behavior of callus pieces immersed 21 hours in solutions of various soaps A to K. Difference between the weight increase of a callus moiety immersed in soap solution and the weight increase of the control moiety immersed in water Table VI Influence of Drying Time on Weight Loss Differences (%) from Original Weights Drying Time, Hours 1 3 4.5 5.5 48 120 1.7% soap E --4.6 --12.2 Water 3.3 --7.2 2.5% soap E 15.8 11.6 3.8 Water 14.7 6.7 0.8 2.4% soap H 78.3 --8.8 Water 23.9 -- 10.4 Minus sign indicates weight loss. The graphic representation (Fig. 5) shows the per cent difference between a callus half swollen in soap solution and one swollen in water during the drying cycle. Immediately after immersion, the lines in Fig. 5 are long, indicating a great difference in weight increases. As drying time progresses, the lines become shorter, indicating that soap and water- soaked callus halves tend to reach the same weight gain or weight loss as compared to their original weight. The spread in weight loss after drying 5 days between the callus piece tested in soap solution and the control callus piece immersed in water becomes very small. Figure 6 shows the difference between one moiety of callus piece immersed in soap solution and the corresponding moiety immersed in water. The values were recorded after a drying ti•ne of 5 days. All soaps did not behave identically: Soaps C, D, E, F, and I reverted after dry- ing for 5 days to a slightly lower weight in the experimental callus half when compared to the control half. These values indicate that slightly more water-solubles were extracted from the callus pieces immersed in

148 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS lOO 5 MIN. 1 HOUR 5 DAYS DRYING TIME Figure 5. Drying cycle of callus pieces immersed 21 hours in soap solutions. Upper end of one of the vertical lines indicates the weight increase of the experimental half immersed in a particular soap solution, while the lower end indicates the weight increase of the corresponding control half immersed in water 'J']0 ' -10- l l ß ß i i ß l C D E F G H I K Figure 6. Weight of callus moieties immersed 24 hours in soap solution after completion of the drying cycle. Difference in per cent between moiety immersed in soap solution and moiety immersed in water as compared with original callus moiety weight. (Various commercial soaps coded C to K drying time, 5 days) soap solution than from the controls. On the other hand, with callus pieces immersed in soap solutions G, H, and K, it was found that after drying for 5 days, there was a slight weight gain as compared to the con- trol. In these cases, there probably was absorption of soap constituents in the callus, compensating for the amounts of solubles which had been extracted. Repetitive soaking of callus in soap solutions at room temperature provided the results shown in Table VII. The second immersion in soap solution did not cause additional weight loss.