A thermal analysis study of hydroxy benzoic acid derivatives using rising temperature thermogravimetry

Hydroxy benzoic acids were subjected to rising temperature thermogravimetric analysis. After optimizing the procedural variables, the kinetics of decomposition was determined and methyl paraben was taken as the calibration compound to characterize the evaporation patterns for the ortho and meta derivatives. The E-act values for ortho, meta and para derivatives were 64.8, 78.2, and 119.1 kJ mol(1), respectively. The Antoine and Langmuir equations were utilized to determine the coefficient of evaporation k, which was 124525 +/-0.8, units being in the SI system. The vapor pressure plots were generated for the ortho and meta derivatives; DeltaH(vap) for these two compounds were obtained as 66.7 and 80.4 kJ mol(1), respectively.