A DSC study, supplemented by X-ray diffraction measurements, was carried out on potassium soaps from n.tridecanoate to n.eicosanoate in the range between room temperature and the isotropic liquid region. The present results are combined with earlier ones for the shorter homologues down to methanoate to draw a rather comprehensive picture of the phase relationships concerned. The significant features shown for a number of transition series by plots ΔS vs the number of carbon atoms, as well as the dimorphism exhibited by tridecanoate at room temperature are also discussed.