WATER HOLDING CAPACITY OF CALLUS 269 25 ø C., while the vapor pressure of glycerol, under the same conditions, is 0.0 mm. (25, 26), it appears reasonable that propylene glycol vapor was absorbed by the glycerol-water mixture in the base of the humidity chamber, and that propylene glycol from the sample continued to vaporize. When the experiments with propylene glycol and with callus -3- propylene glycol were repeated in a constant humidity chamber maintained with a known propylene glycol-water mixture (25), the phenomenon of weight loss after c =Glycerol x-----xPropylene Glycerol i • .... c•Callus zt ........... • Sorb•tol Crystals I 2 :5 4 5 6 7 Time Days Figure 2.--Comparative rates of moisture sorption by glycerol propylene glycol, crystalline sorbitol and unwashed callus (Lot #2) at45% R.H. at 23øC. 4- 2øC. reaching peak value was also observed but to a much lesser extent. The results for propylene glycol and mixtures of this material with callus in Table 2 are the maximum weights observed in the propylene glycol-water chamber when measured daily and may be in error by + 2 per cent. Anhydrous sorbitol picks up only trace quantities of water vapor and has little if any effect on the water pickup of callus, even when stored at 60 per cent R.H. at room temperature for a two-week period. It is well known that a 70 per cent sorbitol solution is a commonly used humectant. There-

270 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS fore, the water sorption of a mixture of powdered callus and 70 per cent sorbitol solution was studied. However, in both series, the sorbitol solu- tions and the callus q- sorbitol mixtures immediately lost weight and con- tinued to lose weight daily, and these studies were discontinued. These results are not surprising since a 70 per cent sorbitol solution is in hygro- scopic equilibrium with air having a relative humidity of approximately 76 per cent and thus should lose water at lower relative humidities (27). TABLE 5--MoIsTUP. E SOKPTION OF WASHED CALLUS,* GLYCEP. OL AND THree. M•XTUV. ES AT 45% R.H. AT 23 ø 4- 2øC. •-----Composition, gm. Callus Glycerol Moisture Absorbed at --- Equilibrium, %- , Found Calculated 0.1349 ... 7.9 ... 0.1702 8.2 ... ... 0.¾i62 18.5 ... 0.6962 18.5 0.'1'1'82 0.4768 15.5 1¾.• 0.1103 0.4607 15.4 16.5 * Lot #2 ww. In Table 5, moisture sorption data for washed callus (Lot #2 ww) and its mixtures with glycerol is shown. This data demonstrates the complete absence of any potentiation of moisture pickup by washed callus in the presence of glycerol and thus is in agreement with the more extensive data on unwashed callus given above. C. The Removal of I4/ater-Soluble Components from Callus and lhe I4/ater Sorption of I4/ashed Callus It was mentioned above that the water-soluble components of callus affect its water-holding capacity (3, 10). It appeared important to deter- mine how different methods of grinding and washing alter the water sorp- tion of callus. Two methods of washing callus for complete removal of water-soluble components were investigated. One of these involved washing with a polar solvent and water, while the second utilized only water. About 10 g. of 60 mesh or finer (Wiley milled callus, Lot #3) was dried to constant weight in a vacuum desiccator over P205. The callus was accurately weighed and shaken intermittently with 100 ml. of a 1:1 mixture of ethyl alcohol and ethyl ether in a glass-stoppered flask for twenty-four hours. The solvent was removed by filtration, and the callus was air dried for three hours. The powdered callus was then washed with consecutive 100 ml. portions of distilled water until the wash water no longer reacted to the ninhydrin and biuret tests. Four such washings were required. The solvent extract was evaporated to dryness on a steam bath. The aqueous extracts were combined and reduced in volume by vacuum distillation at room temperature and retained for the