Excess energy of polymorphic states or glass over the crystal state by heat of solution measurement
Autori: Johari G.P., Salvetti G., Tognoni E., Tombari E.
Affiliazione autori: CNR IFAM,Via del Giardino, 7 – 56127 Pisa, Italy; Department of Materials Science and Engineering. McMaster University, Hamilton, Ont. L8S 4L7, Canada
Abstract: The excess internal energy of one polymorph of a material over another may be determined from their heat of solution in a given solvent. (This energy is not to be seen as reversible heat of transformation of the polymorphs.) Thus the difference between the internal energy of amorphous and crystalline forms of sucrose, glucose and glucose monohydrate have been determined from measurement of their heat of solution in water. These differences are 21.2, 15.5 and 28.1 kJ mol(-1), respectively. This difference in energy is caused by differences in van der Waals interaction energy, the extent of and the total energy associated with H-bonding in the two solids, and their vibrational frequencies. The implication of these studies and further use of the procedure are discussed in general terms, and it is proposed that this method is more accurate than the usual method of integrating heat capacity-temperature data. The method can be used for determining the excess energy at 0 K of materials which decompose or melt incongruently, and when neither the heat capacity of the high temperature phase nor the heat of phase transformation can be measured.
Giornale/Rivista: THERMOCHIMICA ACTA
Volume: 285 (2) Da Pagina: 243 A: 252
Parole chiavi: heat of solutionDOI: 10.1016/0040-6031(96)02915-2Citazioni: 18dati da “WEB OF SCIENCE” (of Thomson Reuters) aggiornati al: 2023-09-17Riferimenti tratti da Isi Web of Knowledge: (solo abbonati) Link per visualizzare la scheda su IsiWeb: Clicca quiLink per visualizzare la citazioni su IsiWeb: Clicca qui