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

Hydroxy benzoic acids were subjected to rising temperature thermogravimetri c analysis. After optimizing the procedural variables, the kinetics of deco mposition was determined and methyl paraben was taken as the calibration co mpound to characterize the evaporation patterns for the ortho and meta deri vatives. The E-act values for ortho, meta and para derivatives were 64.8, 7 8.2, and 119.1 kJ mol(1), respectively. The Antoine and Langmuir equations were utilized to determine the coefficient of evaporation k, which was 1245 25 +/-0.8, units being in the SI system. The vapor pressure plots were gene rated for the ortho and meta derivatives; DeltaH(vap) for these two compoun ds were obtained as 66.7 and 80.4 kJ mol(1), respectively.