EMULSION VEHICLES AND VASOCONSTRICTOR ACTIVITY 147 • & 0% Petrotetu • /• 10% Petroteturn (0.06) ß 2:0% Petro[eturn 30% PetroLeturn [#9 32' :50 28 26 #2 (0.19) (0,35) #3 (0.35) #tt (0.57) #4 (0.57) 5 O.88) X 40% Petrototum 0 50% Petro[otum [] 60% Petroletum ß 70% Petro[etum ( ) Oi[/Weter Phase-Volume Retio # Formule Number 22 #36 #34 2O t8 0 #18 #t2 (0.88) (0.88) 24 [1.34) #19 #t3 (t.34) •8 (3.59) #7 (3.59) •20 •30 (2.10) •14 (3.59) {z.lo) {2'1ø) I I I I I I t0 20 30 40 50 60 70 % Mineral Oil Figure 1. Consistency of the 36 hydrocortisone 17-valerate 0.2% o/w emulsions. latum or mineral oil. Formulas #32 and #35 were excluded from further studies be- cause of their physical instability. Two formulas representing extreme conditions, # 1 and #36, were added to the study for comparison. A direct weight loss determination was then conducted on the selected twelve formulas in order to quantify the amount due to evaporation loss at ambient conditions. Figure 3

148 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS LIJ #• .06) #9 O. 19) #27 ß 0% Petro[(]tum ZX t0% Petro[(]tum ß 2:0% Petrot(]tum O 30% Petrot(]tum [] 40% PetroR]tum ß 50% Petrol.(]tum ,t 60% Petrooe(]tum I • 70% Petro•(]tum i • ( } Oil/W(]ter Ph(]se-Volume #2 (0.t9) (0.35) #4 Rotio (0.57) # Formule Number (o'.35) #•l (o 8a•,,• #6 ' - • (t34) #4: 0.88) • ,8) (0.88) i- ".z•44)- #43 % (•,34) • (1.34) •7 N (2.10} (2.10) • (3.59) •5 •8 (3.59) (3.59} •34 • 5Z L2' I•,,,•, • •30 #26 (3.59) (3.59) #36 (3.59) #33 (3.59) •35 (3.59} I tO O 20 30 40 50 60 70 % Minerel 0i[ Figure 2. Water evaporation rate (WE) and the percentage of mineral oil in the test o/w emulsions. demonstrates the volatility of the selected twelve emulsions in four hours at ambient conditions. The results in Figure 3 agree well with those of Figure 2. The formulas with the greatest amount of water have the greatest weight loss. From a practical viewpoint, the evaporation of water from the skin or emulsions into the atmosphere is a continuous process. The vehicle effect due to water evaporation will