202 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Surfactant Oil Water 8urfactant ... POE ( 5 mols ) nonylphenyl ether Oil... Liquid paraffin Condition... after standin.q 7 days at 37øc(7 -•7) S ..- homogeneous solubilization region H... heterogeneous reftion e.g. two-layer solubilization system emulsion system a mixture of emulsion and solubilization system Figure 2. An example of the records of observation F•XPERIMENTAL RESULTS The results of observations made after 1 day (1-RT) and 7 days (7-RT) at room temperature and after 1 day (1-37) and 7 days (7-37) at 37øC for each surfactant will be presented. With the POE oleyl ether type (Fig. 3a), the S region is relatively wide, and this type of surfactant is effective for the solubilization of liquid paraffin. The POE lauryl ether type (Fig. 3b), on the whole, is similar to the preceding POE oleyl ether type. The POE lauryl ether type surfactant gives a some- what smaller S region than the POE oleyl ether type surfactant with the same number of ethylene oxide molecules. For the POE nonylphenyl ether type (Fig. 3c), with the 4- and 5-molecule ethoxylates as a boundary, the S region moves from the left side (the oil-rich system) of the triangular diagram to the right side (the water-rich system). Such a tendency is generally noted for other types of surfactants. This type of surfactant gives a not-too-wide S region. The H region, however, frequently consists of the two-layer solubilization system that is, although this type of surfactant pos3esses a strong solubilizing power, it tends to form a complex solubilization system separating into two layers. The POE octylphenyl ether type (Fig. 3d), in general, resembles the POE nonylphenyl ether type. The S region is not very wide. The optimum number of ethylene oxide (EO) molecules for solubilization with the POE dinonylphenyl ether type (Fig. 3e) appears to be ten (the 10-molecule ethoxylates). This type gives a very wide S region and is suited for forming the homogeneous solubilization system.

SOLUBILIZATION OF THREE-COMPONENT SYSTEM 203 1-37 1-RT 7-37 7-RT Oil Figure 3a. POE oleyl ether Figure 3b. POE lauryl ether