Transitiometric Determination of the Phase Diagram of KNO3 between (350 and 650) K and at Pressures up to 100 MPa

A P, T-phase diagram for KNO3 has been experimentally determined over the temperature range from (350 to 650) K and at pressures up to 100 MPa with the use of a scanning transitiometer. These new results are. compared with those reported by other authors. The comparison shows that the pressures and temperatures of transitions among phases I, II, and III obtained in this study are in good agreement with those reported in the literature. In addition, a detailed analysis of these transitions was performed by measuring simultaneously the enthalpy and volume changes at selected pressures both by heating and cooling. The results demonstrate the reliability of scanning transitiometry to study phase transitions in complex systems at high temperatures and pressures. The present data will serve using KNO3 as a calibrating and reference substance in subsequent high-pressure high-temperature studies by scanning transitiometry.