156 JOURNAL OF COSMETIC SCIENCE White oil • ureth4 • L2 + Whiteoil t.cc+w•.• L2 + LLC + V•nite oil LLC+White oi!+H20 a,O+LLC LLC Water Laureth 4 Figure 4. Phase diagram of water/white oil/Laureth 4. L2: solubility area. LLC: lameliar liquid crystal. the two three-phase regions in the diagram (LLC + L 2 + S1) connects the LLC, isotropic liquid (L2), and solid region (S1). The second region (LLC + S• + H20 ) connects the water with S• and LLC. The five two-phase regions consist of (L2 + S•), (LLC + S•), (LLC + L2), (H20 + LLC), and (H20 + S•). Figure 2 shows the phase diagram of o•-hydroxyoctanoic acid/water/white oil. The diagram shows one solid regions (S•), one three-phase region (H20 + white oil + S•), and the two two-phase regions (H20 + S1) and (S• + white oil). The maximum amount of white oil that could be added to S• was 41.8 wt%. The phase diagram of the white oil/Laureth 4/o•-hydroxyoctanoic acid system is shown in Figure 3. The solid region (S•) extends up to 41.8 wt% white oil and 31.4 wt% Laureth 4, as the Laureth 4 and white oil are mutually soluble in each other, with an insignificant amount of o•-hydroxyoctanoic acid dissolved. Hence, the rest of the phase diagram becomes a two-phase region, S• and Laureth 4 white oil solution. The tie lines of the two phases are shown in Figure 3.

PHASE BEHAVIOR OF ot-HYDROXYOCTANOIC ACID 157 Laureth 4 Water B A 2 White oil 2-hydroxyoctanoic acid Figure 5. Three-dimensional phase diagram of the total system. O: sample A. I: sample B. S: solid area. L2: solubility area. LLC: lameIlar liquid crystal. Region 1: isotropic solution with oil/surfactant at 90/10 wt. ratio. Region 2: isotropic solution with oil/surfactant at 80/20 wt. ratio. Region 3: isotropic solution with oil/surfactant at 70/30 wt. ratio. The phase behavior of the water/white oil/Laureth 4 system (Figure 4) shows one isotropic region (L2) , where white oil and Laureth 4 are totally miscible in each other, with a maximum solubility of water of 15 wt%. The liquid crystal region solubilized up to 7.8 wt% of white oil. There are two three-phase regions: one region connects white oil to LLC and L 2 (L 2 + LLC + white oil), and the second region connects water, white oil, and the LLC phase (LLC + H20 + white oil). There are three two-phase regions in this diagram: (H20 + LLC), (LLC + white oil), and (LLC + L2). The tie lines of two-phase regions are shown in Figure 4 connecting LLC and L 2. Figure 5 shows essential features of the four components ot-hydroxyoctanoic acid/water/ white oil/Laureth 4. The interlayer spacing results from the Laureth 4 with water lameliar liquid crystal are given in Figure 6. Increasing the ratio of Laureth 4/ot- hydroxyoctanoic acid leads to an increase in the slope of the linear relation between the interlayer spacing and the volume ratio of water, but a decrease in the interlayer spacing when extrapolated to zero water content. Figure 7 gives the interlayer spacing upon adding the white oil. Adding 5% white oil does not effect the d o value, but the slope