Accurate determinations of excess heat capacities,CpE, of liquid and solid phases with respect to composition and temperature are shown to be possible by direct reaction calorimetry. The results are compared with those obtained by heat capacity measurements and departure from the additivity rule. In the case of solutions, the knowledge ofCpE with respect to concentration permits a pertinent analysis of the short-range order. Some results concerning binary alloys, such as In-Te, Cu-Sb and Ag-Te, are given.
Classical thermo-analytical micro methods (DTA, DSC) are still very useful for process work, but medium scale instruments based on heat flow measurement are attaining an increasingly important role in this domain.
As in many areas, development of reaction calorimetry for industrial applications was driven by needs and by available means (technical capabilities).
The needs have been fairly constant over the past decades. There are data needs:
-Heat release rates
-Heat of desired reactions and decompositions
-Heat capacities and heat transfer capacities
It took the specialists of calorimetry a long time to recognize and to accept the operational needs, namely:
-Working under controlled temperature conditions (constant temperature, temperature ramps)
-Adding components during runs (continuously or in portions)
-Simulation of industrial mixing conditions
The main driving force for the development of process oriented calorimetric instruments was the evolution of electronic hardware which made the control of heat flow on a (non micro) laboratory scale easy.
The paper gives an overview on the principles of heat flow control and reviews the developments of the fifties and sixties, when the matching of heat flow with heat release by reactions was the goal.
With the advent of fast and powerful laptop computers, the focus has shifted. Now, the deduction of true heat release rates from signals which may be badly distorted, is the goal.
Some recent developments are reviewed and the hope is expressed that calorimetric equipment, inexpensive enough to be affordable for every laboratory engaged in process work, will be available soon.
An attempt is made to develop a calorimetric method by taking full advantage of the differential possibilities offered by the Tian-Calvet calorimeter. This method is intended to measure the enthalpic parameter, defined as the limiting value (dilute solutions) of the derivative of the partial enthalpy of mixing with respect to the concentration, in liquid In-Bi alloys. The results, although rather scattered, exhibit a systematic discrepancy when compared with those obtained by the classical direct reaction calorimetry method with the same calorimeter. They are in better agreement with the values estimated from simple thermodynamic models.
Authors:Manuel Ribeiro da Silva, Luís Santos, Ana Faria, and Filipa Sistelo
The molar heat capacity and the standard (p0 = 0.1 MPa) molar enthalpies of formation of the crystalline of bis(glycinate)lead(II), Pb(gly)2; bis(dl-alaninate)lead(II), Pb(dl-ala)2; bis(dl-valinate)lead(II), Pb(dl-val)2; bis(dl-valinate)cadmium(II), Cd(dl-val)2 and bis(dl-valinate)zinc(II), Zn(dl-val)2, were determined, at T = 298.15 K, by differential scanning calorimetry, and high precision solution-reaction calorimetry, respectively. The standard
molar enthalpies of formation of the complexes in the gaseous state, the mean molar metal–ligand dissociation enthalpies,
Authors:Dragana Živković, Aleksandra Mitovski, Ljubiša Balanović, Dragan Manasijević, and Živan Živković
Terpilowski et al. [ 9 ] and Cakir et al. [ 10 ], while Kleppa [ 11 ], Wittig et al. [ 12 ], and Yazawa et al. [ 13 ] expolored them using direct reactioncalorimetry, and newest reference by Brunetti et al. [ 14 ]. Optimal thermodynamic activities for indium
Authors:Gaochao Fan, Zaiyin Huang, Junying Jiang, and Li Sun
grade. The experimental procedure consists of two steps: (i) synthesis and characterization of the ZnO nanosheets; (ii) reactioncalorimetry of the ZnO nanosheets reaction system and the bulk ZnO reaction system.
A typical synthesis process is as
Authors:Amar M. Ait, M. Idbenali, N. Selhaoui, K. Mahdouk, A. Aharoune, and L. Bouirden
peritectic formation was reported, respectively, at 1623, 1568, and 1523 K.
Selhaoui and Kleppa [ 7 , 8 ] measured the standard enthalpies of formation of Ru 2 Y and Ru 2 Y 5 by direct reactioncalorimetry at high temperature. The values obtained
standard molar enthalpy of formation of the title compound at T = 298.15 K have been measured by adiabatic calorimetry and isoperibol solution-reactioncalorimetry, respectively. The experimental values of molar heat capacities have been fitted to a
Authors:Y. P. Liu, Y. Y. Di, W. Y. Dan, and D. H. He
an isoperibol solution-reaction calorimeter.
Solution-reactioncalorimetry is one of the classical methods to obtain the standard molar enthalpy of dissolution at infinite dilution and the dissociation enthalpy of coordination ion of many