SOLUBILIZATION OF THREE-COMPONENT SYSTEM 207 (1-RT, 7-RT, 1-37, and 7-37) were made for each sample for a total of 14:4: observations. The number of observations occurring in the homo- geneous solubilization system was then expressed in per cent. n/N X 100 •-percentage of S region where N • 144 n = number of observations occurring in the homogeneous solubilization system Table II Percentage of the S Region EO Molecule Percentage Optimum Surfactant Number HLB • of S Region Point POE oleyl ether 5 6.7 54 10 10.0 56 0 20 13.5 19 POE lauryl ether 3 6.4 30 5 8.7 54 0 10 12.1 22 20 15.5 12 POE octylphenyl ether 3 5.8 12 5 8.2 15 0 10 11.5 4 20 14.9 2 POE nonylphenyl ether 3 5.4 17 4 6.7 36 0 5 7.8 26 7 9.4 34 10 11.1 4 20 14.6 0 POE dinonylphenyl ether 5 5.3 10 l0 8.7 59 0 20 12.0 26 POE dioleate 9 5.4 5 18 8.9 57 0 36 12.5 23 POE sorbitan monooleate 3 8.6 13 5 9.8 15 0 10 12.0 13 20 14.5 6 •HLB was calculated by Kawakami's equation (2). With the S region of the surfactant having the optimum EO molecule number located at the center of the triangular diagram, the S region extends symmetrically toward the left (the oil-rich region) when the number of EO

2O8 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 37øC POE oleyl ether 5mols 10mols (•)'"H Region •".S Region POE lauryl ether 5tools POE nonylphenyl ether 3mols 5mols 7mols POE dinonylphenyl ether 10mols POE oct¾1phen¾1 ether 5mols POE dioleate 18mols Figure 4. Results of observations after one month ..... 1.1...POE oleyl ether ..... 1.2'-'POE lauryl ether •--0 2.1...POE octylphen¾1 ether ---' 2.2.'. POE nonylphenyl ether •---02.3--' POE dino.n¾1- phenyl ether "--"3.1... POE dioleate * .... 4.1.-. POE sorbitan monooleate Figure 5. Percentage of the S region molecules decreases and towards the right (the water-rich region) when the number increases. This can be represented schematically as in Fig. 6. A comparison of the sizes of the S region at the optimum HLB for solubilization indicates that the S region of POE nonylphenyl ether is not very wide, whereas that of POE dinonytphenyl ether is very wide. Because of this, additional experiments were carried out on POE (7 mols) monooleate