346 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (2) McBain, J. W., "Colloid Science," Boston, D.C. Heath and Co. (1950). Kruyt, H. R., "Colloid Science," Vol. I, Amsterdam, Elsevier Press (1952), p. 340. (3) Gurwitsch, L., "Wissenschaftliche Grundlagen der Erdolbearbeitung," London, Transla- tion by Moore, Chapman and Hall (1932), p. 430. (4) Raschevsky, N., Z. Physik, 46, 568 (1928). (5) Stackelberg, M. v., Klockner, E., and Mohrhauer, P., Kolloidzschr., 115, 53 (1949). (6) Davies, J. T., and Haydon, D. A., Proc. 2rid Intern. Congress Surface •tctivity, Butter- worths, London 1, 417 476 (1957). (7) Davies, J. T. and Rideal, E. K., "Interfacial Phenomena," New York, Academic Press, Inc. (1961). (8) McBain, J. W., and Woo, T. M., Proc. Roy. Soc. (London), 163A, 182 (1937). Kaminski, A., and McBain, J. W., Ibid., 198A, 447 (1949). (9) Haydon, D. A., Nature, 176, 839 (1955). Lewis, J. B., and Pratt, H. R. C., Ibid., 171, 1155 (1953). (10) Pospelova, K. A., and Rehbinder, P. A., •tcta physicochima. U.R.S.S., 16, 71 (1942). (11) van der Waarden, M., •7. ColloidSci.,7, 140 (1952). (12) Ilkovid, I., Collection tray. chim. tch•coslov., 4, 480 (1932). (13) Langmuir, I., Cold Spring Harbor Symposium, 6, 193 (1938). (14) Cockbain, E.G., and Schulman, J. H., Trans. Faraday Soc., 36, 651 (1940). (15) Matalon, R., Ibid., 46, 674 (1950). (16) Kaminski, A., and McBain, J. W., Proc. Roy. Soc. (London), 198A, 447 (1949). (17) Davies, J. T., Bell, G., and Law, P. J. S., Research Project in Dept. of Chemical Engineering, Cambridge (1960). (18) Hartung, H. A., and Rice, O.K., 5•. Colloid Sci., 10, 436 (1953). A SURVEY OF DR. J. T. DAVIES' CONTRIBUTIONS TO EMULSION STABILITY, FOAM STABILITY AND OLFACTORY THRESHOLDS OF ODORANTS T•E s'rut)•Es of J. T. Davies have contributed very significantly to the understanding of several phenomena highly important to cosmetic chemists. His recent work has led to the development of equations for predicting emulsion stability, foam stability and olfactory thresholds of odorants. Earlier workers had shown that an electrical charge an a monolayer might bring about radical changes in its free energy and surface tension. As early as 1951 (1), as a result of his extensive studies of interfacial po- tentials and reactions, Davies had shown that surface potentials (2) and the amounts and rates of adsorption (4) are also affected by the electrical charge, and had developed an equation of state for oil-water films. In 1956 (8) he developed a similar expression to cover charged monolayers at the air-water interface. In 1957 (10) Davies reported data, obtained by using a new viscous- traction surface viscometer of his own design, which showed a correlation between foam stability and surface viscosity. In the same year he evolved a quantitative kinetic theory of emulsion type, which provided a firm basis for the HLB system of classifying emulsifiers (11). The HLB num- ber was shown to depend upon the ratio of the coalescence rate of the oil-in-

346 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (2) McBain, J. W., "Colloid Science," Boston, D.C. Heath and Co. (1950). Kruyt, H. R., "Colloid Science," Vol. I, Amsterdam, Elsevier Press (1952), p. 340. (3) Gurwitsch, L., "Wissenschaftliche Grundlagen der Erdolbearbeitung," London, Transla- tion by Moore, Chapman and Hall (1932), p. 430. (4) Raschevsky, N., Z. Physik, 46, 568 (1928). (5) Stackelberg, M. v., Klockner, E., and Mohrhauer, P., Kolloidzschr., 115, 53 (1949). (6) Davies, J. T., and Haydon, D. A., Proc. 2rid Intern. Congress Surface •tctivity, Butter- worths, London 1, 417 476 (1957). (7) Davies, J. T. and Rideal, E. K., "Interfacial Phenomena," New York, Academic Press, Inc. (1961). (8) McBain, J. W., and Woo, T. M., Proc. Roy. Soc. (London), 163A, 182 (1937). Kaminski, A., and McBain, J. W., Ibid., 198A, 447 (1949). (9) Haydon, D. A., Nature, 176, 839 (1955). Lewis, J. B., and Pratt, H. R. C., Ibid., 171, 1155 (1953). (10) Pospelova, K. A., and Rehbinder, P. A., •tcta physicochima. U.R.S.S., 16, 71 (1942). (11) van der Waarden, M., •7. ColloidSci.,7, 140 (1952). (12) Ilkovid, I., Collection tray. chim. tch•coslov., 4, 480 (1932). (13) Langmuir, I., Cold Spring Harbor Symposium, 6, 193 (1938). (14) Cockbain, E.G., and Schulman, J. H., Trans. Faraday Soc., 36, 651 (1940). (15) Matalon, R., Ibid., 46, 674 (1950). (16) Kaminski, A., and McBain, J. W., Proc. Roy. Soc. (London), 198A, 447 (1949). (17) Davies, J. T., Bell, G., and Law, P. J. S., Research Project in Dept. of Chemical Engineering, Cambridge (1960). (18) Hartung, H. A., and Rice, O.K., 5•. Colloid Sci., 10, 436 (1953). A SURVEY OF DR. J. T. DAVIES' CONTRIBUTIONS TO EMULSION STABILITY, FOAM STABILITY AND OLFACTORY THRESHOLDS OF ODORANTS T•E s'rut)•Es of J. T. Davies have contributed very significantly to the understanding of several phenomena highly important to cosmetic chemists. His recent work has led to the development of equations for predicting emulsion stability, foam stability and olfactory thresholds of odorants. Earlier workers had shown that an electrical charge an a monolayer might bring about radical changes in its free energy and surface tension. As early as 1951 (1), as a result of his extensive studies of interfacial po- tentials and reactions, Davies had shown that surface potentials (2) and the amounts and rates of adsorption (4) are also affected by the electrical charge, and had developed an equation of state for oil-water films. In 1956 (8) he developed a similar expression to cover charged monolayers at the air-water interface. In 1957 (10) Davies reported data, obtained by using a new viscous- traction surface viscometer of his own design, which showed a correlation between foam stability and surface viscosity. In the same year he evolved a quantitative kinetic theory of emulsion type, which provided a firm basis for the HLB system of classifying emulsifiers (11). The HLB num- ber was shown to depend upon the ratio of the coalescence rate of the oil-in-