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  • 1 Dalian Institute of Chemical Physics, Chinese Academy of Sciences Thermochemistry Laboratory Dalian 116023 P.R. China Dalian 116023 P.R. China
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As one primary component of Vitamin B3, nicotinic acid [pyridine 3-carboxylic acid] was synthesized, and calorimetric study and thermal analysis for this compound were performed. The low-temperature heat capacity of nicotinic acid was measured with a precise automated adiabatic calorimeter over the temperature rang from 79 to 368 K. No thermal anomaly or phase transition was observed in this temperature range. A solid-to-solid transition at T trs=451.4 K, a solid-to-liquid transition at T fus=509.1 K and a thermal decomposition at T d=538.8 K were found through the DSC and TG-DTG techniques. The molar enthalpies of these transitions were determined to be Δtrs H m=0.81 kJ mol-1, Δfus H m=27.57 kJ mol-1 and Δd H m=62.38 kJ mol-1, respectively, by the integrals of the peak areas of the DSC curves.