EMULSIONS AND FOAMS 391 (22) Kitchener, J. A., and Mussellwhite, P. R., The Theory of Stability of Emulsions, in Sherman, P., Emulsion Science, Academic Press, New York, 1968, Chap. 2. (23) Becher, P., Emulsions: Theory and Practice, 2nd Ed., Reinhold Publishing Corp., New York, 1965. (24) Verwey, E. J. W., Electrical double layer and stability of emulsions, Trans. Faraday Soc., 36, 192 (1940). (25) Bikcrman, J. J., Foams: Theory and Industrial Applications, Reinhold Publishing Corp., New York, 1953. (26) Sanders, P. A., Complex formation in aerosol emulsions and foams. II. Nonionic sur- factants (polyoxyethylene fatty ethers) and polar compounds, Soap Chem. Spec., 43, 68, 70 (July, Aug., 1967). (27) Cosmetic Bulletin "Brij" Surfactants (Polyoxyethylene Fatty Ethers), Atlas Cheinical Industries, Inc., 1964. (28) Sanders, P. A., Aqueous alcohol aerosol foams, Drug Cosmet. Ind., 99 (Aug., Sept., 1966). (29) Sanders, P. A., The nature of the aqueous alcohol foam system, Aerosol Report/aer 8, 202 (May, 1969), Freon© Aerosol Report A-75, E. I. du Pont de Nemours and Co., Wilmington, Del. (30) Sanders, P. A., New developments in aerosol foams, Amer. Perrum. Cosmet., 81, 31 (Feb., 1966). (31) Kitchener, J. A., and Mussellwhite, P. R., The Theory o[ Stability o[ Emulsions, in Sher- man, P., Emulsion Science, Academic Press, New York, 1968, Chap. 2. (32) Martynov, V. M., The Theory of emulsions. II. Density of emulsions as function of the degree of dispersity, Kolloid. Zh., 11, 255 (1949). (33) Cockbain, E.G., The aggregation of oil particles in emulsions, Trans Faraday Soc., 48, 185 (1952). (34) Dixon, J. K., Salley, D. J., Argyle, N. A., and Weith, A. J., Measurement of the adsorp- tion of surface-active agents at a solution/air interface by a radiotracer method, Proc. Roy. Soc. (London), 203A, 42 (1950). (35) Dixon, J. K., Salley, D. J., Judson, C. M., and Argyle, N. A., Radiotracer study of cationic surface-active agents by measurement of gegnion adsorption, J. Chem. Phys., 19, 378 (1951). (36) Defoy, V. J.,Thermodynamics of thin lavers. J. Chim. Phys. 46, 375 (1949). (37) Derjaguin, B. V., and Landau, L., Theory of the slability of strongly charged lyophobic sols and of the adhesion of strongly charged particles in solutions of electrolytes, Acta. Phys. Chim. USSR, 14, 633 (1941). (38) Davies, J. T., and Rideal, E. K., Inter{acial Phe•omer•a, 2nd Ed., Academic Press, New York and London, 1963, Chap. 5. (39) Drost-Hansen, W., Aqueous Inter{aces, in Ross. S.. Chemistry arid Physics of Inter[aces, American Chemical Society Publications, Washington, D.C.. 1965. Chap. 4. (40) Henniker, J. c., The depth of the snrface zone of a liquid. Rev. Mod. Phys., 21, 322 (1949). (41) McBain, J. W., Colloid Science, D.C. Heath and Co.. Boqon. 1950. (42) Low, P. F., Physical Chemistry of Clay-Water D•teraclio•s. in Norman, A. G, Advances ir• Agronomy, Vol. 13, Academic Press, New York and I•ondon. 1961.

J. Soc. Cosmet. Chem., 21, 393-415 (May 27, 1970) Prediction and Evaluation of Emulsion Stability with Ultracentrifugal Stress* EDWARD R. GARRETT, Ph.D.* Presented in part September 9, 1969, Seminar, St. Louis, Mo. Synopsis--The hypothesis that the SVEDBERG RELATIONS for the FLOTATION of OIL PARTICLES in high ratio OIL/WATER EMULSIONS do not hold is substantiated. UL- TRACENTRIFUGATION of such emulsions introduccs a nonlinearity into log oil cicarance rs. time plots which is due to the subsequent sweep-out of the heterogencous discontinuous phase since slippage and stratification of particles are blocked. NONSTRATIFIED CREAMS demonstrate an initially apparent first-order process of large particle drainage from. the cream concomitant with continuous drainage of heavier surfactant. The final rate of oil separa- tion is constant and reflects that rate-determining coalescence is at the cream-oil interface, that the ultimate cream is a tightly packed, homogeneously particulate mass with mininmm continuous phase. This was substantiated by microscopic examination. In addition to reproducible preparative methods, sensitive analytical methods have been devcloped to assay the SURFACTANT and oil concentrations in various cmulsions. INTRODUCTION Although centrih•gation has been considered in a casual manner in the evaluation of the stability and properties of emulsions, little quan- titative study has been effected until recent use of the modern analytical * Work supported by Grant GM-12099-01, 02, 03 from the National Institutes of Health, U.S. Public Health Service, Bethesda, Md. t College of Pharmacy, J. Hillis Miller Health Center, University of Florida, Gainesville, Fla. 32601. 393