COMPLEX FORMATION IN AEROSOLS 817 7'riethanolamine Laurate •¾ystems Systems which caused the Inost rapid wetting generally had the highest drainage rates. In the tri- ethanolamine laurate series, the foams from triethanolamine laurate or those with oleyl or stearyl alcohols wetted paper almost immediately after discharge. These foams also had the highest drainage rates. Foams with lauryl, myristyl, or cetyl alcohols did not wet paper for over an hour. The effect of the alcohols upon foam persistence followed a somewhat similar pattern. The foams from triethanolamine laurate alone, or in combination with oleyl or stearyl alcohols, started to collapse within 30 minutes after discharge. Foams with lauryl, myristyl, or cetyl alcohols retained their structure for over an hour. Triethanolamine g•[yristate Systems -All of the alcohols increased the stability of triethanolamine myristate foams. The foam from trierhanoi amine myristate wetted paper immediately, but none of the foams con- taining lauryl, myristyl, cetyl, stearyl, or oleyl alcohol wetted paper during one hour after discharge. These results correlate with the foam drainage results. Although the foam from triethanolamine myristate alone showed rapid drainage, it maintained its structure for over an hour but became progressively thinner. The foams with lauryl and oleyl alcohols showed some thinning after 30 minutes. The most stable foams were obtained with myristyl, cetyl, and stearyl alcohols. Triethanolamine Palmitate and Stearate Systems--Foams from tri- ethanolamine palmirate or stearate also wetted paper immediately, followed by those that contained lauryl alcohol. It must be remem- bered that the triethanolamine palmkate and stearate systems have a soap concentration only one-fourth that of the laurate and myristate systems. The foams with myristyl, cetyl, or stearyl alcohols did not wet paper for at least two hours. Those wetting results again correlate well with the foam drainage data. The foams from triethanolamine palmirate or stearate alone col- lapsed after about one hour those with lauryl alcohol became increas- ingly thinner as a result of drainage but maintained their structures for at least two hours. Foams with myristyl, cetyl, or stearyl alcohols de- veloped slight surface crazing during two hours but otherwise showed little change. One of the most interesting effects of the alcohols in the triethanol- amine palmirate or stearate series was upon the product discharge. All of the systems gave a liquid or semiliquid discharge which sub-

818 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS sequently expanded into a [oanL However, the rate at which the product expanded into a foam after it had been discharged was a function of the chain length of the alcohol. For example, the discharge from triethanolamine stearate alone expanded almost immediately into a foam, and was followed by that with lauryl alcohol. The discharge Table IX Effect of Various Alcohols upon Properties of Triethanolalnine-Fatty Acid Syste•ns Fatty Acid Alcohol Emulsion Properties Foam Properties Viscosity Stability Stability Drainage Stiffness Laurie Lauryl x xx xx - - x Myristyl x xx xx - - xx Cetyl xx xx xx - - x Stearyl x xx o o o Oleyl o o o - - o Cholesterol x xx - o Myristic Lauryl xx xx x - - o Myristyl xx xx xx - - o Cetyl xx xx xx - - o Stearyl x xx x Oleyl x xx x o Cholesterol xx xx Palmitic Lauryl o o x o o Myristyl xx xx xx - - o Cetyl xx xx xx - - o Stearyl xx xx xx - - o Cholesterol x xx o - Stearic Lauryl o o o o o Myristyl x xx xx - - Cetyl xx xx xx - - o Stearyl xx xx xx - - o Cholesterol xx xx - o - x = Positive effect. xx = Pronounced positive effect. o = Essentially no effect. - -- Negative effect. - - = Pronounced negative effect. from the system containing myristyl alcohol required still more time to expand into a foam, and that with stearyl alcohol required almost five minutes for expansion into a foam. The rate at which the liquid dis- charges expand into a foam may be an indication of the relative strength of the molecular complexes. The strongest complexes might be expected to show the most resistance to expansion during vaporization of the propellant after the product had been discharged. The foam density also increased in the triethanolamine stearate/