Melting of Benzoic Acid in Mixtures with Various Organic Compounds after Plastic Deformation under High Pressure

Abstract

Mixtures of benzoic acid with various organic compounds are subjected to plastic deformation in Bridgman anvils under a pressure of 1 GPa at room temperature. The influence of high-pressure plastic deformation on the calorimetric behavior of the deformed layer of benzoic acid in mixtures with various organic components is studied under conditions of thermal treatment (programmed heating at a constant rate). The parameters for the process of melting of deformed layers of benzoic acid mixtures depending on the chemical composition are studied by differential scanning calorimetry (DSC). In all cases, the melting point T_m decreased by 5–8 deg. The melting enthalpy both can increase by 1.7 times and decrease by 2.3 times. In mixtures with organic indicators, the melting enthalpy of the acid depends on the pH of the indicator and reaches 750 J g^–1 in a mixture with Congo red.