CORRELATION OF INTERFACIAL FREE ENERGY IN BINARY AND TERNARY SYSTEMS

A general correlation which may be used to estimate interfacial tension in binary and ternary systems is based on treatment of the interfacial region as one of finite thickness. By assuming the interface concentration gradient as a linear function of thickness, a correlation is developed between interfacial tension and the reciprocal solubility of the two bulk phases in contact. The presence of a third solute serves to increase the interface thickness, lowering the interfacial tension. Data considered are those for six ternary systems, taken as part of this work, and 27 binary systems, including one nonaqueous system, from the literature. The equations enable the prediction of interfacial tension to within 12%, using known values of molecular parameters and bulk concentrations. For the present, temperature effects have not been considered. © 1969, American Chemical Society. All rights reserved.