A new experimental technique using calorimetric measurements to establish solid-liquid equilibrium (SLE) phase diagrams of binary systems of organic compounds with complete immiscibility in the solid phase is presented. Unlike some methods previously reported in the literature it is not based in the identification of the phase transition temperatures at different compositions of the mixture. Instead it measures the changes on the relative size of the liquid phase during the fusion of a mixture, that is later converted into a phase diagram using the lever rule. This technique, while somewhat less accurate than some processes based in the direct detection of phase transitions for measuring SLE phase diagrams, is much faster and presents an accuracy similar to other calorimetric techniques. It also makes possible to define the position of invariant points, such as the eutectic or peritectic, both in composition and temperature, or the composition of intermediate compounds, with a single calorimetric measurement.