AbstractGas‐liquid chromatography is a separation method for volatile compounds which is widely used in analytical chemistry. It is based on the partition of the components of a sample between a moving gas phase and a stationary liquid phase of low volatility, the latter in the form of a thin coating on inert support particles filling a long, narrow column. Under proper conditions, values of the standard partial molar free enthalpy of vaporization from infinitely dilute solution in the stationary phase can be obtained from retention times, as a function of temperature. Combination with the standard molar free enthalpy of vaporization of the pure compounds yields the standard partial molar free enthalpy of mixing with the stationary phase. As a method for the investigation of the thermodynamics of interactions in polymer solutions, gas‐liquid chromatography is unique in the sense that it easily yields accurate data at a mole fraction of the polymer near unity and at high temperature. Here the method is applied to solutions of some normal and branched alkanes in polyisobutylene. The results are discussed in terms of a simplified version of the Prigogine solution theory, used by Patterson et al., and in terms of the solution theory of Flory, Orwoll, and Vrij.