ABSORPTION OF CHEMICALS ON SKIN Table VII Repetitive Sorption and Desorption of Callus Immersed in 20% Solutions of Soaps E, D, and K 149 Weight Loss• (%) Soap E D K After 1st immersion of 21 hours After 2nd immersion of 4 hours 12.2 10.5 7.9 11.1 10.4 3.1 After 5 days' drying. All values based on original weight of particular callus piece. Table VIII Comparison of Weight Increases of Callus Moieties Immersed in Water and Hexylene GlycoN Treatment Swelling (%) Dehydration (%) Distilled water 97.0 34.9 Hexylene glycol (40% aqueous) 120.8 70.3 Immersion for I hour, drying for 30 min. Effect o/ Humectants Hexylene glycol and polyethylene glycol were investigated alone and in combination with soap. Of two halves of a callus piece immersed for the same length of time (and dried for the same length ot• time), the one immersed in hexylene glycol solution retained water faster and [cr a longer time than the control (Table VIII). It was t•ound that callus halves immersed in a mixture ot• soap, hexyl- ene glycol, and water also retain water faster and longer than the cor- responding halves immersed in distilled water (Fig. 7). When compared with the effect of soap alone, the humectant in combination with soap did not seem to have an additive effect. The humectant even decreased the amount o[ swelling and water absorption which was enhanced by soap. At a higher level ot• humectant, we ob- served less total absorption, but longer retention of water in the callus and apparently permanent retention of the humectant in the callus (Table IX). Immediately following the 20 hours' immersion, the callus piece which was soaked in the mixture showed less weight gain than the control soaked in water. Throughout the drying stage, however, the callus piece which was immersed in the mixture showed a higher weight gain than the control.

150 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 3ooj 100[ • j 2 HOURS 70 HOURS ß WATER 1% SOAP, [] 20% HEXYLENE GLYCOL [] 1% SOAP IMMERSION TIME Figure 7. Weight increase versus immersion time for excised callus immersed in water, immersed in soap, and immersed in a mixture of 1% soap and 20 % hexylene glycol in water Table IX Weight Increases•of Callus Immersed for 20 Hours in Mixture of Soap, Hexylene Glycol, and Water, and Dried Weight Change ø (%) Drying Time 5 min 4 hours 5 days Water 226.0 4.4 -- 10.5 Mixture s 188.5 55.9 27.5 O. 8% soap, 50% hexylene glycol, and 49.2% water. Minus sign indicates weight loss. Table X Influence of Humectant on the Water-binding Capacity of Stratum Corneum Weight Change s (%) Drying Time 5 min 70 min 5 days 1st Immersion (5 hours) Water 153.5 O. 9 -- 15.8 20% glycol 147.5 13.9 --4.1 50% glycol 34.5 8.3 -- 1.5 2nd Immersion (4 hours) Water 123.0 --3.5 --29.8 20% glycol 117.0 O. 6 --9.9 50% glycol 9.2 1.9 --7.8 s Of callus moieties immersed in distilled water and in polyethylene glycol. Minus sign indicates weight loss.