The transformation of the energy equation from the mass average to the volume average reference frame exposes a pseudo Dufour effect. The theoretical model for absorption into a stagnant liquid including this effect, the heat of absorption, variable density, an interfacial velocity, and an arbitrary equilibrium condition at the interface is able to predict experimental data over a wide range of conditions. The data consisted of liquid temperature profiles and mass transfer rates into a stagnant liquid. The ammonia-water system exhibited interfacial temperature rises from 6.9°K to 18.2°K. The interfacial temperature rise for the propane-decane system was 1.3°K. Simpler theoretical models were able to predict the mass transfer rates or the temperature profiles.