COMPLEX FORMATION IN AEROSOLS 819 alcohol series as the molecular weight of the alcohol increased. Again, this effect may be related to the strength of the molecular complex. Microscopic ]•xamination--Microscopic examination of the tri- ethanolamine laurate and triethanolamine laurate/lauryl alcohol foams did not reveal any marked differences, although the presence of lauryl alcohol appeared to cause a slight decrease in bubble size. However, the addition of cetyl alcohol to triethanolamine palmitate systems or the addition of stearyl alcohol to triethanolamine stearate foams caused a very noticeable decrease in bubble size. This effect of the molecular complexes upon the bubble size of the foams is similar to that noted with the sodium lauryl sulfate foams. The effect of stearyl alcohol in decreasing the bubble size of triethanolamine stearate foams is illustrated by the microphotographs in Figs. 6 and 7. These foams had the com- positions described in Table VII. The effect of cholesterol upon the bubble size of foams was opposite to that observed with the long-chain alcohols. Cholesterol caused a noticeable increase in bubble size. This is illustrated by the micro- photographs in Figs. 8 and 9 of triethanolamine palmirate systems with and without cholesterol. The data in Table VIII also show that cho- lesterol decreased foam stiffness, which again is an effect opposite to that found with long-chain alcohols. These two effects, the increase in bubble size and the decrease in foam stiffness, suggest that the triethanol- amine-fatty acid/cholesterol complex is very fluid, and during discharge the vaporization of the propellant into a gas expands the film more than when cholesterol is not present. This would explain both the increase in bubble size and the decrease in foam stiffness. Variation in Alcohol Concentration The effect of increasing concentrations of alcohol with triethanol- amine laurate/lauryl alcohol and triethanolamine myristate/myristyl alcohol systems is shown in Tables X and XI. In the triethanolamine laurate system, increasing concentrations of lauryl alcohol caused an increase in emulsion stability and a decrease in foam drainage. There was a slight tendency toward increasing foam stiffness. Increasing lauryl alcohol concentration also increased foam stability. The foams with no lauryl alcohol or with a soap/lauryl alcohol ratio of l:•/g wetted paper immediately after discharge. That with a soap/ alcohol ratio of l:lff2 wetted paper in about 25 minutes, and the foam with a soap/alcohol ratio of l:a/g wetted in about an hour. These re- sults correlated essentially with the foam drainage results.

82O JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table X Variation in Lauryl Alcohol Concentration-Triethanolamine Laurate Systems Laurate•/Lauryl Emulsion Properties Alcohol Ratio Drainage (Mols) Viscosity Stability (60 min) Foam Properties •,c Stiffness (g) 1: 0 Low 1-5 min 86.0 1: •/• Low 30-60 rain 83.0 1: •/• Low 60 min 65.0 1: •/• Low 16 hr 40.0 1:1 Low to medium 16 hr 11.0 8 10 16 18 22 Triethanolamine laurate concentration = 0.10 21//. All discharges were quiet. All foam densities ranged from 0.062 to 0.063 g/cc. Table XI Variation in Myristyl Alcohol Concentration-Triethanolamine Myristate Systems Myristate•/ Emulsion Properties Alcohol Ratio (Mols) Viscosity Stability Foam Properties • Drainage Stiffness Type of (3 hr) (g) Discharge 1:0 Low 15-30 rain 1: •/• Low 5 hr 1: •/• High 5 hr 1: • High 5 hr 1:1 High 5 hr 56 42 Quiet 2 45 Quiet 1 42 Slightly noisy 0 52 Noisy 0 56 Noisy Triethanolamine myristate concentration = 0.10 Foam densities ranged from 0.064 to 0.069 g/cc. Table X[I Variation in Propellant-Triethanolamine Laurate/Lauryl Alcohol Systems Propellant Foaxn Properties Emulsion Properties Drainage Stiffness Density Viscosity Stability (60 min) (g) (g/cc) Type of Discharge Freon-12 Freon-12/Freon-114 (40/60) Freon- 114 Freon- 12/Freon- 11 (50/50) Propdlant 142b Propellant 152a Low to 5 hr 4 18 0.052 medium Low to 5 hr 4 21 0. 065 reediron Low to 5 hr 2 26 0. 067 reediron Low to 5 hr 44 8 I! 053 medimn Low ,5 hr 65 12 0. 042 Low to 5 hr 3 14 O. 036 medium Quiet Quiet Quiet --semi- liquid .Quiei Noisy Noisy