THERMODYNAMICS OF MICROEMULSION FORMATION .3. ENTHALPIES OF SOLUTION OF WATER IN CHLOROFORM AS WELL AS CHLOROFORM IN WATER AIDED BY CATIONIC, ANIONIC, AND NONIONIC SURFACTANTS

Outlines of complex ternary phase diagrams of cetyltrimethyl ammonium bromide/water/CHCl3, cetylpyridinium chloride/water/CHCl3, sodium bise thylhexyl sulfosuccinate/water/CHCl3, and octylphenoxy polyoxyethylene ether/water/CHCl3 systems have been presented. Enthalpies of solution of water-in-oil + amphiphile and oil-in-water + amphiphile media have been calorimetrically determined. Except for cetyltrimethylammonium b romide/water/CHCl3 system, all the systems have exhibited thermal inve rsion for water and oil dispersion near the phase separation point. Th e surfactant concentration at the inversion point bears a linear corre lation with the concentration of the dispersed solvent. The thermodyna mics of solubilization of the solvents in the form of microdroplets ar e presented. The measured heat capacities of all the systems agree ver y reasonably with the calculated values assuming ideal mixing behavior Of the components. (C) 1997 Academic Press.