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- Title
Low-temperature heat capacities and standard molar enthalpy of formation of aspirin.
- Authors
Xu, F.; Sun, L.-X.; Tan, Z.-C.; Liang, J.-G.; Di, Y.-Y.; Tian, Q.-F.; Zhang, T.
- Abstract
Molar heat capacities (Cp,m) of aspirin were precisely measured with a small sample precision automated adiabatic calorimeter over the temperature range from 78 to 383 K. No phase transition was observed in this temperature region. The polynomial function of Cp,m vs. T was established in the light of the low- temperature heat capacity measurements and least square fitting method. The corresponding function is as follows: for 78 K≤T≤383 K, Cp,m)/J mol-1 K1=19.086x4 + 15.951X³ - 5.2548X² + 90.192X + 176.65, [X=(T-230.50/1 52.5)]. The thermodynamic functions on the base of the reference temperature of 298.15 K, {ΔHT - ΔH298.15} and {Sr-S298.15}, were derived. Combustion energy of aspirin (ΔcUm) was determined by static bomb combustion calorimeter. Enthalpy of combustion (ΔcHm0) and enthalpy of formation (ΔfUm) were derived through ΔcUm as - (3945.26±2.63) kJ mol-1 and - (736.41±1.30) kJ mol-1, respectively.
- Subjects
ASPIRIN; ENTHALPY; HEAT of formation; THERMAL analysis; CALORIMETRY
- Publication
Journal of Thermal Analysis & Calorimetry, 2004, Vol 76, Issue 2, p481
- ISSN
1388-6150
- Publication type
Article