200 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS of cosmetics and a correlation of the present study with that on emulsification of liquid paraffin carried out earlier by the same authors ( 1 ) is intended. 2-Octyl dodecanol and squalane were used in addition to liquid paraffin in the experiments designed for a study on a correlation between the optimum HLB in the emulsion system and that in the solubilization system. With a triangular diagram and oil, water, and surfactant represented at each corner of the triangle, the effects of factors such as the surfactant type, number of ethylene oxide molecules in the surfactant, aging, and aging temperature on the appearance of the solubilization region were studied. The term "solubilization system" here means the system in which oil is homogeneously and transparently dispersed in water or vice versa. EXPERIMENTAL METHOD Oils and Surfactants Used Liquid paraffin (Saybolt viscosity of 70 at 100øF) was mainly used as the oil. Twenty-seven surfactants were chosen from seven types which are regarded as having a relatively strong solubilizing power according to the experiences of the authors (Table I). All oils and surfactants used were commercial brands and were not specially refined for the present experiments, because the experimental results were to be used in actually preparing cosmetics where correlation of results would be necessary. Table I Surfactants Used 1. POE • alkyl ether type POE olcyl ether POE lauryl ether 2. POE alkylaryl ether type POE octylphenyl ether POE nonylphenyl ether POE dinonylphenyl ether 3. POE fatty acid diester type POE dioleate 4. POE sorbitan monoester type POE sorbitan monooleate N o =5, 10, 20 mols N=3, 5, 10, 20 N=3, 5, 10, 20 N=3, 4, 5, 7, 10, 20 N=5, 10, 20 N=9, 18, 36 N =3, 5, 10, 20 •POE, polyoxyethylene. ON, munber of ethylene oxide (EO) molecules.

SOLUBILIZATION OF THREE-COMPONENT SVSTEM 201 Surfactant O i 10 20 30 40 50 60 70 80 Water • IO vvater NO. oil% water% surfactant% 1 10 10 80 2 2O 10 70 3 10 2O 70 34 3O 60 10 35 20 70 10 36 10 80 10 Figure 1. Triangular diagram of oil-water-surfactant Compoxitionx and Method of Preparation The triangular diagram representing oil, water, and surfactant at its three corners was drawn for each surfactant as shown in Fig. 1, and the compositions corresponding to 36 points in the diagram were prepared. This means 36 compositions were prepared with each of 27 surfactants, making a total of 972. A 200-g sample was prepared for each composition as follows: Oil, water, and surfactant were weighed into the same beaker and heated at 70øC to effect solution. The sample was agitated by means of an Eppenbach type Homo-mixer (1/6 hp), operated at 10,000 rpm [or 1 rain, and cooled to 30øC in an ice water bath while stirring with a propeller-type agitator. Those samples which were too viscous to undergo the Homo-mixer treatment were excepted from this treatment. Testing Method Determination of thc solubilization type (O/W or W/O) and the emulsion type (O/W or W/O) and visual ewfiuation were made on each sample. Determination of the type was made with electric conductivity device? For visual observation, the sample was filled in two ground-glass- stoppered cylinders with 50 graduations one of the filled cylinders was left standing at room temperature and the other in a thermostat maintained at 37øC. The sample kept at room temperature was observed after 1 day, 7 days, 1 month, and 6 months, and the sample kept at 37 øC in the thermostat was observed after 1 day, 7 days, and 1 month. Appearance of a solubiliza- tion system was recorded. An example of the records is shown in Fig. 2. * Japan Argano Co., 5-5-16 Hongo, Bunkyo-Ku, Tokyo,