THE SEVENTH SPECIAL AWARD 341 EXAMPLES OF MECHANISM (ii) \Ve have eliminated the first mechanism for emulsions formed spon- taneously from solutions of methanol or ethanol in toluene, placed gently in contact with water prevention of the turbulence has but little effect on the emulsification. Further, the interfacial tension is always positive, of the order 10 dynes cm., leaving mechanism (ii) by default. This can be confirmed bv presaturating the toluene-alcohol mixture with water the diffusing alcohol leaves much water stranded in the oil, as well as oil stranded in the water. This mechanism is likely whenever the third component increases considerably the mutual solubility of the oil and the water: thus mixtures of an oil with sulfonated castor oil and sodium oleate, placed in contact with water, emulsify by the diffusing sodium oleate carrying oil with it into the water (10). The same explanation (6, 7) also fits the spontaneous emulsification seen when a solution in petrol-ether of commercial sodium dodecyl benzene Figure 1.--Drop of toluene containing 10% ethanol, formed in pure water. The drop is oscillating vigorously, and the emulsion is thrown off in turbulent eddies. Flash photograph (6).

342 JOURNAL OF THE SCOIETY OF COSMETIC CHEMISTS sulfonate is gently placed in contact with pure water (11). The rapid diffusion of the detergent into the water carries with it some oil, which is then "stranded" in the water as the detergent becomes more diluted. Further, some of the water, which initially becomes solubilized in the oil- detergent solution, apparently becomes "stranded" in the oil as more Figure 2.--Drop of toluene containing 10/% ethanol, formed in water containing a trace of surface-active agent. The spontaneous emulsion streams smoothly from the drop. Flash photograph (6). detergent leaves the oil for the water, and small amounts of w/o emulsion are thus visible (6). Emulsions may thus be formed on both sides of the interface. In these experiments a temperature of 90øC. must be main- tained to ensure a sufficient solubility of the detergent in the oil. Even when the interfacial tension is as high as 5 dynes cm. -•, the emulsification is still marked.