A conceptual, but concise, account of the nature of the partition gas chromatographic separation process, from the view point of thermodynamics and with special reference to entropy changes, is presented. Based on a philosphical and qualitative approach, illustrated through simple physical principle, the treatment embodies the quantitative aspects of the problem as well. This has been taken up with regard to the free energy of dilution, or for that matter, the entropy of mixing and unmixing. Furthermore, the quantitative contributions of the carrier gas and the liquid stationary phases to the overall entropy changes have been derived for a binary system, whereby the analysis reveals the isentropic nature of the chromatographic separation process.