L•IPONITE CLAY--A SYNTHETIC INORGANIC GELLING AGENT 247 Acetone/water The results art shown in Fig. 8. The main difference between acetone Figure 8 150e•-•.. e • 50-- • I 0 i z 3 4 5 Clay concentration, % •"O•o ?% clay -- _ -- I I o 0-5 1.o Sodium concentration, me - 20 -- 50 0 -- 60 -- 70 Effect of clay and electrolyte concentration on acetone/water (40/60) systems I õOe-•=•••• • ß ß ioo 50- I I 2 3 4 5 Clay concenlratian, % '% clay o 0.5 i-o Sodium concentration, me -io -- 20 -- :•0 .-- -- 40 (3. -- 50 0 -- 60 -- 70 trigtt, re ,9 Effect of clay and electrolyte concentration on ethylene glycol/water (50/50) systems

248 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS and the alcohols is that the electrolyte tolerance of the former is higher at 40% concentration. In fact, acetone at 40% behaves similarly to the alcohols at 250/0 . Ethylene glycol/water Fig. 9 shows that very similar properties are obtained with 50% ethylene glycol to those given by acetone at 400/0 . Glycerol/water The results for the glycerol/water system shown on Fig. 10 differ from all previous ones in that the ESS values are much higher for all corres- ponding compositions. This cannot be accounted for by the higher vis- cosity of the medium. Most of the optical densities could not be measured owing to bubble inclusion, as mentioned before. According to visual estimation, all the dispersions having varying clay concentration were clear (i.e. the genuine OD would be less than 10) those having added electrolyte were cloudy from 0.4 me g-1 upwards. The electrolyte tolerance is higher than that of all previous systems investigated, though the concentration of the organic compound is the highest. This is presumably because the tests were done at lower than the maximum possible concentration, as was observed when 25% alcohol was used instead of the maximum possible (about 40%). 150•,• , 50 - 0 I 2 3 4 5 0 0.5 1.0 Cloy concentration, % Sodium concentration, me g-• 30 5O 0 60 Figure 10 Effect of clay and electrolyte concentration on glycerol/water (60/40) systems