104 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (4) H. R. Moskowitz, Fragrance intensity measurement by magnitude estimation, Perfumer and Flavorist, 1, 18-25 (Oct./Nov. 1976). (5) H. R. Moskowitz, Sensory measurement: The rational experience--Its use, limitations and prospects, MBA Technical Quarterly, 14, 111-119 (1977). (6) W. S. Cain and H. R. Moskowitz, Psychophysical Scaling of Odor, in "Advances in Chemorecep- tion," J. Johnston, Jr., D. Mouton and A. Turk, Academic Press: New York, N.Y., 1974 Vol. III, pp 2-32. (7) H. R. Moskowitz, C. N. Dubose and Reuben, Flavor chemical mixtures - a psychophysical analysis, paper presented at the symposium, •Objective Measurement of Flavor Quality," R. Scanlan, Ed., American Chemical Society: California, 1977 pp 29-44. (8) B. Berglund, U. Berglund and T. Lindvail, On the principle of odor interaction, Acta Psychologica, 35, 255-268 (1973). (9) H. R. Moskowitz and C. Barbe, Profiling of odor components and their mixtures, Sencory Processes, 1, 212-226 (1977). (10) W. S. Cain, Odor intensity: Mixtures and masking, Chemical Senses and Flavor, 1,339-352 (1975).

j. Soc. Cosmet. Chem., 30, 105-125 (March/April 1979) Antifoams R. D. KULKARNI, E. D. GODDARD and M. R. ROSEN Union Carbide Corporation, Tarrytown Technical Center, Tarrytown, NY 10591. Received August I, 1978. Synopsis A general background on the subject of ANTIFOAMS is presented which includes their classification, preparation and testing. Emphasis is given to silicone-based compositions whose introduction in this field some three decades ago led to major changes in antifoaming technology. Fundamental mechanisms involved in the antifoaming process are outlined and a description is given of some of the mechanisms of foam stabilization. Lastly, a new, experimental antifoam, of "transient character," is described and its possible applications are outlined. Its activity in aqueous foaming systems lasts for a limited period thereafter the full foaming power of the solution is restorod. INTRODUCTION A foam is an aggregate of bubbles. More precisely, it is a dispersion of gas in a liquid where liquid forms the continuous phase. The phenomenon of foaming is primarily governed by the properties of the interfaces involved and foaming is always accompanied by an increase in the interfacial area of the system and hence its total energy. Thus, in a strict thermodynamic sense, foams are basically unstable and are therefore self-destroying. Their formation requires a net input of energy. The ease of their formation or their stability is, among other factors, determined by the gas/liquid interfacial energy. Pure liquids do not foam and therefore, for foaming, at least one more component is required. For persistent foams one needs the presence of a surface active ingredient. In most practical systems the foam stabilizing component is either a soluble surfactant, a finely divided solid, or both. While the mechanism of foam stabilization is not well understood, the role of solids, in particular, is least understood. Nevertheless it is well recognized that foams derive their stability by offering resistance to the external as well as internal stresses that can cause foam destruction. For reviews on the subject of foam stabilization see references 1-7. Depending upon the conditions prevailing in the solutions, a generated foam can span a remarkable range of stabilities, which can vary from milliseconds to almost unlimited duration. In many practical operations foams last long enough to interfere with physical or chemical processing and this has warranted the development of meap,_s for 105