Figure 8. Photomicrograph of a triethanola•nine pahnitate foam Figure 9. Photomicrograph of a triethanolamine palmitate/cholesterol foam

824 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Increasing the concentration of the triethanolamine myristate/ myristyl alcohol complex increased emulsion viscosity, emulsion stabil- ity, and foam stiffness. The foams with either soap/alcohol concen- tration were fairly stable and, except for a slight surface crazing, changed very little in two hours. Variation in Fatty .4 cid/ Triethanolamine Ratio Free fatty acids are normally present in solutions of the salts of fatty acids as a result of hydrolysis. These free fatty acids have been reported to form molecular complexes with the salts under certain cir- cumstances. As previously mentioned, sodium stearate and stearic acid have been shown to form such complexes. The triethanolamine salts of the fatty acids, which are salts of weak bases and weak acids, would also hydrolyze to form free fatty acids. Complexes between the free fatty acids and the triethanolamine salts might be formed in the aerosol systems. It was hoped to obtain evidence for the existence of such complexes in the triethanolamine-fatty acid systems by changing the concentration of free fatty acid. Samples were prepared in which the ratios of fatty acid to triethanolamine were 1:1.5 and 1.5:1. In the first system, there was an excess of the triethanolamine, and in the second system there was an excess of the fatty acid. If the aerosol system containing the higher concentration of fatty acid exhibited the usual properties Table XIII Effect of Variations in Soap Alcohol Concentrations • Salt Concentration in Aqueous Phase 0.025 M 0.100 M Triethanolamine Laurate/Lauryl Alcohol Emulsion viscosity Low Low to medium Emulsion stability 1 rain 5 hr Foam drainage (60 rain) 20 6 Foam stiffness (g) 20 20 Type of discharge Quiet Quiet Density (g/co) 0.06 0.06 Triethanolamine Myristate/Myristyl Alcohol Emulsion viscosity Low High Emulsion stability 1-5 min 5 hr Foam drainage (60 rain) 2 0 Foam stiffness (g) 24 56 Type of discharge Liquid--noisy Noisy Density (g/cc) 0.13 0.07 Soap/alcohol ratio (molar) = 1:1.