Phase diagram of mixtures of stearic acid and stearyl alcohol

Stearyl alcohol (98.4%), stearic acid (96.0%) and their binary mixtures were investigated by differential scanning calorimetry (DSC) at a heating and cooling rate of 10 K min−1. The phase diagrams on heating and cooling were constructed and showed a eutectic behavior for the solid–liquid equilibrium line. In the heating phase diagram, the eutectic line was not always visible due to the existence of a phase transition in the solid state. A shift in the eutectic phase composition towards the acid was observed on cooling. The cooling and heating phase diagrams further differed in the fact that only two exotherms were observed during cooling where three endotherms were observed during heating. A plot of the enthalpy of the mixtures versus the mole fraction shows that different processes are involved in the solid state.