COLLOIDAL MAGNESIUM ALUMINUM SILICATE IN COSMETICS 255 an increase in solids and therefore a greater concentration of charges and a firmer gel structure, suspension is improved. Moreover, Magnesium Aluminum Silicate has a higher ap- parent viscosity than would be ex- pected from the solids content. This property of increased apparent viscosity which can be reversed by simple agitation is called thixo- tropy (11). Thixotropyis a definite advantage in suspensions and is greatly responsible for the superior- ity of Magnesium Aluminum Sili- cate over organic gums which form irreversible gels. Magnesium Alu- minum Silicate can suspend at lower viscosity than organic gums and can suspend more efficiently at equal viscosity. Suspensions of talc in Magnesium Aluminum Silicate, algin, high vis- cosity carboxymethyl cellulose, and tragacanth each at 65 cp. were ob- served. Magnesium Aluminum Sili- cate suspended 100 per cent of the talc, algin 75 per cent, and carboxy- methyl cellulose and tragacanth 30 per cent. Similar results were ob- tained with suspensions of colloidal sulfur. • C.M.C. tSET TO .o. Sodium Alginate JELLY • METHYL CELLULOSE et ACACIA - • TRAGACANTH .•o ,- M.A.S. 18 4•0 60 100 % SALTS SUSPENDED Figure 3 In another study (see Fig. 3), a 3 per cent total of bismuth salts was suspended in Magnesium Aluminum Silicate and in several organic gums. A 1 per cent dispersion was used in all but one case. Carboxymethyl cel- lulose •and sodium alglnate formed solid ii•reversible gels with the salts entrapped, and free water released. Methyl cellulose, acacia, and traga- canth showed hard packing that could not be redispersed by shaking, whereas, Magnesium Aluminum Sili- cate remained flowable and gave 60 per cent suspension. With a 21/2 per cent Magnesium Aluminum Silicate dispersion, 100 per cent sus- pension was obtained in a free flow- ing system. Before concluding, we must men- tion that the limitation of time has not allowed discussion of many other interesting and useful properties of Magnesium Aluminum Silicate. Some of these are: (1) capacity for base exchange, (2) acid neutraliza- tion, (3) formation of films, (4) lu- bricating, disintegrating, and bind- ing of tablets. Magnesium Aluminum Silicate is non-toxic. Detailed studies on mice and rabbits have been made and these data are available. This paper has attempted to ex- plain the behavior of Magnesium Aluminum Silicate with the hope that an understanding of how it ß functions will promote the most ad- vantageous use of the product. BIBLIOGRAPHY (1) Hawley, Gessner G., "The Story of Col- loids" New York, Alfred A. Knopf, 1947 p. 30.

256 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (2) Marshall, C. Edmund, "The Colloid Chemistry of the Silicate Minerals," New York, Academic Press Inc., 1949, p. 69. (3) Ibid., p. 70. (4) Ibid., p. 162. (5) Conley, John E., "Bentonire," Wash- ington. D.C., U. S Bureau of Mines, Techmcal Paper 609, 1940, p. 3. (6) Ibid., pp. 12, 13. (7) Caldwell, O. G., and Marshall, C. E., "A Study of Some Chemical and Physi- cal Properties of the Clay Minerals Nontronite, Attapulgite and Saponite," Columbia, Mo., U. of Missouri Res. Bul. #354, 1942, pp. 27, 28. (8) Clark, F. W., "The Constitution of the Natural Silicates," U.S. Geological Survey Bul., 588, 109 (1914). (9) Sutheim, George M., "Introduction to Emulsions," Brooklyn, N.Y., Chemical Publishing Co., Inc., 1946, pp. 87, 146. (10) Dorr, J. V. N., and Lasseter, Franklin P., "Colloid Chemistry," New York, N.Y., Reinhold Publishing Corp., 1946, pp. 784, 785 (Alexander Vol. VI). (11) Green, Henry, and Weltmann, Ruth N., "Colloid Chemistry," New York, N.Y., Reinhold Publishing Corp., 1946, p. 328 (Alexander Vol. VI). INDEX TO ADVERTISERS Alrose Chemical Co .................................................. VIII Atlas Powder Company ...................................... Inside Back Cover Baker Chemical Co., J. T ............................................. lI Bjorksten Research Laboratories.. • .................................... XVIII Continental Chemical Company ....................................... X Cosmetic Laboratories, Inc ............................................ XX Emu'sol Corporation, The ............................................ XI Evans Chemetics Inc ................................................ V Firmenich Inc ...................................................... VI Givaudan-De'.awanna, Inc ................................... Inside Front Cover Kohnst•mm & Co., Inc., H ........................................... VII Kolmar Laboratories Inc ............................................. XV Leberco Laboratories ................................................ XIX Maimstrom & Co., N. I .............................................. IX Merck & Co., Inc ................................................... XVI Parento, Inc., Compagnie ............................................ XVII Reheis Co., Inc ..................................................... XXII Schimmel & Co ..................................................... IV Seil, Putt & Rusby, Inc ............................................... XIX Snell Inc., Foster D .................................................. XVIII Summit Chemical Products Corp ....................................... XIV United States Testing Co., Inc ......................................... XVIII Van Ameringen-Haebler, Inc .......................................... XIII Vanderbilt Co., Inc., R. T ............................................. XXI Van Dyk & Company, Inc ............................................. III Ver'ey and Company, Inc., Albert ...................................... I Will and Baumer Candle Co., Inc .............................. Outside Back Cover