288 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS :•.•:•.-.•.•'•:?i•}=• 5 "• •'7- -'? _."-?.•.'• :'¾•"'•,5:i '•,•, "•5•,5•::i{=• '•'. --•.=--•k:5%•-,.7 •-•.' '% • • 5 .... ?•.•.5?•ei::•:•?'?'• "-'•:•'•'.::•,:•5•¾:-": ..•'-•'•,i. ?-? •': -,.'P%: ? ?•.-•: '••:•%•5•%',,s'•'•" •'"'•x• •.•. • Figure 2. Stability of gels in hot water: (a) stable gel (b) unstable 8el (1) X-Ray Analysis.' Two types of X-ray diffractometers, Rotaflex* and JRX-12VA•- were used to elucidate the structures of the surfactants and gels by means of small angle scanning and can/era method at 5 C Targe.t Cu. 2 ø (2) Differential Thermal Analysis (DTA).' The gel sealed in aluminum cell was measured at 0 to 70øC, raising the temperature 2.5øC/rain by a scanning type DSC.* (3) NMR.. Variation of chemical shift with proton in water of the aqueous solution to which various solutes were added, was measured by Hitachi$ R-20 type NMR at 34øC. (4) Phase Inversion Temperature (PIT).' Influence of the addition of amino acids on the PIT was measured with Squalane•Beeswax•POE(6) oleyl alcohol ether 5 per cent (w/w)•water system (volume ratio = 0.6). (5) Heat of Solution.. A sealed ampiale containing about 2 g of the surfactant, Sunsoft O-30B, was broken in 50 g aqueous solution of a.Nino acid having various concentra- tions. of heat on mixing (cal/g) was me'asured by a twin type microcal- orimeter** at 35øC. Evolution (6) Water Content Migration to the Surfactant Phase.' The amount of water migrating into the surfactant (Sunsoft O-30B) through an interface of the surfactant and an *Rigaku Denki 8-2, Kandasurugadai, Chiyodaku, Tokyo, Japan. -•Japan Electron Optics Laboratory, 1418, Nakagami, Akishimashi, Tokyo, Japan •2 Shibanishikubo, Minatoku, Tokyo, Japan. **Applied Electric Laboratory, 4-672 Sekimachi, Nerimaku, Tokyo, Japan.

WATER-IN-OIL EMULSIONS 289 aqueous solution of the amino acids was measured by a MK-A type Karl Fischer ap- paratus •* at 35øC measuring point: 1 cm above the interface (constant). (7) Optical Microscopy.' Emulsion particles were observed by means of phase-contrast and polarizing microscopies magnification 400 x. (8) Electron Microscopy,' Specimens were exposed to the saturated osmium tetroxide at- mosphere for 72 h at 4øC, then dehydrated with ethanol and finally embedded in epoxy resin Epon 812. The specimens were sectioned at 500 • thickness by a LKB III type ultramicrotome equipped with a diamond knife and observed under the Hitachi HU- 12A EM. (c). Inorganic-Organic Property Balance (lOB).' The authors make reference to this con- cept in order to correlate the results of the experiment. Fujita (5) proposed the idea of the inorganic-organic property as a tool for predicting the various properties of or- ganic substances. From the physical properties, such as boiling point, refractive index, etc., he gave an empirically specific number to each inorganic and organic property which corresponded to each functional group. Those surfactants capable of forming gels with an aqueous solution of amino acids or their salts are shown in Table I. Table II Table I Classification of the Surfactants Applicable to Gel Formation Appearance X-Ray Surfactant Diffraction Spacing (_•,) Trade Name Common Name RT lOB Pattern d• d• d=/d• Sunsoft O-30B a Glycerol L 0.39 C 33.8 70.7 2.09 monooleate Arlacel 186 b Glycerol L 0.47 C 33.8 73.9 2.18 monooleate G-ElS Glycerol L 0.42 C 33.8 70.7 2.09 monoisostearate POEM O-72-D c Diglycerol L 0.66 C 32.3 67.7 2.10 dioleate DIG-EIS • D•glycerol L 0.47 C 33.0 67.7 2.05 diisostearate PE-EIS Pentaerythritol L 0.53 C 31.5 67.7 2.15 diisostearate Arlacel 83 b Sorbitan L 0.63 C 34.3 73.9 2.15 sesquioleate Emalex e POE (2.4) sorbitol L 0 49 C 33.8 70.7 2.09 EG2854-ol tetraoleate L: Liquid S: Solid, C: Clear I' Indistinct N: No peak. aTaiyo Kagaku Co., Ltd. (62 Akahori, Yokkaichi, Mie, Japan). bKao Atlas Co., Ltd. (1-I Kayaba, Nihonbashi, Chuoku, Tokyo, Japan). CRiken Vitamin Oil Co., Ltd. (3-8-10 Nishikanda, Chiyodaku, Tokyo,Japan). dMatsumoto Trading Co., Ltd. (3-1 Nihonbashihoncho, Chuoku, Tokyo, Japan). e5 Nihon Emulsion Co., Ltd. (5-32-7 Minami, Koenji, Suginamiku, Tokyo, Japan). rSurfactants synthesized by the authors. *Kyoto Denki, 68 Kisyoinshinden, Minamiku, Kyoto, Japan.