Treatment of excess thermodynamic quantities for liquid mixtures

Thermodynamic data on mixtures of liquids are usually expressed as excess quantities Y-EX and analyzed with the Redlich-Kister equation. This approach can in some cases be misleading and hide strong interactions at low concentrations. In agreement with the original statement of Redlich and Kister, it is therefore better to plot such data as Y-EX/X-2(1 - X-2). This quantity, which is directly related to the apparent molar quantities of both components, is often a more useful quantity and has just as much a thermodynamic significance as Y-EX.