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The dependence of the properties of the three-phase bodies in ternary H20-oil-nonionic amphiphile mixtures on the nature of the oil and the amphiphile is of importance for both research and application.We suggest characterizing these properties by the coordinates 71* (temperature) and 7* (amphiphile weight fraction) of the amphiphile-rich phase (the microemulsion) at equal volumes of water and oil, as well as by the interfacial tension crabl between the aqueous and the oil-rich phase at this point of the phase prism. A relation between these properties is suggested that permits evaluating one of them if the other two are known. Furthermore, it is shown that the dependence of T* on the nature of the oil and the amphiphile is apparently correlated with that of the critical temperatures of the two binary mixtures oil-amphiphile and H20-amphiphile. The results are briefly discussed with respect to the currently proposed phenomenological models of microemulsions.

As we have shown in our preceding publications on the properties of multicomponent liquid systems of the type H20-oil-nonionic surfactant-electrolyte, the phase behavior of such systems is rather similar, irrespective of whether the nonionic surfactants form micelles and lyotropic mesophases or not. In this paper we attempt to explain this finding by suggesting these systems be considered as being near tricritical, i.e., as being sufficiently close to a tricritical point. If this was an approach to reality, their phase behavior would be governed by universal seeding laws irrespective of their particular microstructure. As a first test of this working hypothesis, we have studied the influence of the chemical nature of the oil on the phase behavior of a ternary system with a given nonionic surfactant at 1 bar, by decreasing the hydrophobicity of the oil within a homologous series. It turned out that with particular short-chain surfactants the phase behavior appears to be indeed near tricritical, whereas with long-chain surfactants the tricritical point can apparently only by reached by increasing the pressure. Since an increase of pressure is equivalent to an addition of a hydrotropic electrolyte, we shall, in a forthcoming paper, study the phase behavior of quaternary systems with respect to the above working hypothesis.

In this paper we report on an attempt to quantify the effect of electrolytes on the mutual solubility between H20 and simple nonionic amphiphiles. On the basis of the studies by Schneider and co-workers, we have determined the minimum amount of lyotropic salts necessary to enforce phase separation between H20 and 1-propanol (C3E0), as well as the amount of hydrotropic salts necessary to make the upper loop of the system H20-ethylene glycol monobutyl ether (C4Ei) vanish. The results of the first series of experiments are compared with the Hofmeister series. The latter series of experiments demonstrate that the effect of a hydrotropic electrolyte, whether surface active or not, is quite similar to that of a hydrophilic nonionic amphiphile or that of pressure. The significance of these effects for the discussion of the phase behavior of multicomponent liquid mixtures including oil (microemulsions) is noted.

Ultrasonic relaxation spectra are reported for UCIO4 dissolved in acyclic polyethers of increasing chain length including 1,2-dimethoxyethane (1,2-DME), CH3(OCH2CH2)"OCH3 with = 1; diglyme with = 2; and tetraglyme with = 4. Spectra were measured at 25 °C at various concentrations in the frequency range ~1 to ~500 MHz. The data are analyzed in terms of the dimerization equilibrium 2LiC104 ^(LiC104)2, determining rate constants, equilibrium constants of dimerization, and isoentropic volume changes for the process, 5.Infrared spectra for the t-4 mode of C104™ at approximately 623 cm™* 1 reveal a satellite band at wavenumbers ranging from 633 to 638 cm™1 that is attributed to contact ion pairs. Microwave dielectric relaxation spectra of LiC104 in the above polyethers reveal a relaxation process involving the solute (that is absent in the pure solvent) which is attributed to the rotational relaxation of LiC104 ion pairs. The relaxation process shifts in frequency from around 2 GHz for LiC104 in 1,2-DME to 0.21 GHz for LiC104 in tetraglyme at 25 °C. This behavior correlates well with the change in the viscosity of the solvents which has been determined separately. The apparent dipole diameter is about