Combustion calorimetry on samples of mass less than 10 mg of substances containing iodine with a CRMT rocking-bomb calorimeter. Application to the study ofp-iodobenzoic acid

Abstract

We have used a CRMT rocking calorimeter associated with a microbomb to determine the enthalpy of combustion of a sample of mass less than 10 mg of a substance containing iodine. p-Iodobenzoic acid (p-IC6H4CO2H), a candidate as reference material for combustion calorimetry of substances containing iodine, has been investigated. The value of −(3154.221.3) kJ·mol −1 for its molar enthalpy of combustion obtained with this apparatus is in very good agreement with the only literature value obtained by classical bomb combustion calorimetry. 7

Critical Evaluation of Thermodynamic Properties for Halobenzoic Acids Through Consistency Analyses for Results from Experiment and Computational Chemistry

“…For 2-iodobenzoic acid, the enthalpies of reaction for the gas phase based on the experiment and computation are in excellent agreement, while differences near 10 kJ mol 21 are seen for 3-and 4-iodobenzoic acids. The inconsistency for 3-and 4iodobenzoic acids is surprising, given the general agreement of the combustion results reported by Smith, 117 Sabbah and Rojas Aguilar, 119 and Ribeiro da Silva et al 81 Initial checks of groupadditivity increments for iodine on the aromatic ring of benzoic acid relative to that on benzene were concluded to be successful by Ribeiro da Silva et al 81 Unfortunately, this conclusion was based, in part, on the enthalpies of sublimation reported by Tan and Sabbah, 122 which are now seen to be 14-20 kJ mol 21 lower than mutually consistent values determined with Knudsen effusion 126 and transpiration, 129 and reported subsequently.…”

“…A variety of calorimeters were used in the consistent results, including static bomb calorimetry, 81,117,118 rotating-bomb calorimetry, 81,118 and rocking micro-calorimetry. 115,119 Values reported by Smith 117 in 1956 were recalculations of those reported in the thesis by Karlsson. 120…”

Standard molar enthalpy of formation of 4-iodobenzoic acid by static and rotating-bomb calorimetry

“…This value is also in agreement, within the uncertainties associated, with the other literature values. (5,6) We recommend the adoption of 4-iodobenzoic acid as a test substance in bomb combustion calorimetry of organo-iodine compounds.…”

“…Karlsson (2) measured, by the static-bomb method, the standard massic energy of combustion of the three isomers of iodobenzoic acid and Smith (5) has recalculated the results. For 4-iodobenzoic acid another value has been reported, (6) determined using a rotating-bomb calorimeter.…”