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Instrumentation and calibration of the Calvet calorimeter

Enthalpy of solution of PrBr3 at standard conditions

Journal of Thermal Analysis and Calorimetry
Authors: Beata Salamon, Jan Kapała, and Marcelle Gaune-Escard

values is insignificant. However, for the calculation of the enthalpy of solution the values of calorimeter constant were used separately. The quality of heating the reference material was controlled by analysis of the temperature dependence of

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Abstract  

The heats of solution of tetrabutylammonium bromide have been measured in mixtures of formamide (FA) with methanol (MeOH) and ethylene glycol (EG) at 313.15 K by calorimetric method. The standard enthalpies of solution in binary mixtures have been extrapolated to infinite dilution by Redlich–Rosenfeld–Meyer type equation using the literary data at 298.15 K and the present paper data at 313.15 K. The Debye–Hückel limiting law slope A H required for calculation of the ∆sol H 0 value has been obtained with application the new additive scheme of determination of the physic-chemical characteristics of binaries. The scheme is tested on the example of Bu4NBr solutions in FA–MeOH mixture at 298.15 K. Its application yields the ∆sol H 0 value very closed on the ones determined with the real (non-additive) characteristics of binaries. The standard enthalpies of solution extrapolated by Redlich–Rosenfeld–Meyer type equation are in a good agreement with the ones computed in terms of the Debye–Hückel theory in the second approximation. The heat capacities characteristics of Bu4NBr have been calculated in H2O–FA, MeOH–FA and EG–FA mixtures using the literary and present data. The sequence of solvents H2O > FA > EG > MeOH located on their ability to solvophobic solvation found by us earlier for enthalpic characteristics is confirmed by the ∆C p 0 values. The comparison of thermochemical characteristics of Bu4NBr solutions in aqueous and non-aqueous mixtures containing FA has been carried out. The own structure of water remains in the region of small additions of formamide to co-solvents. It considerably differs the H2O–FA mixture from the investigated non-aqueous systems.

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examined mixture were calculated by the extrapolation of the measured enthalpies of solution Δ sol H as a function of square root of molality m to m = 0: where A is an experimental slope. The

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-component systems can be calculated from the enthalpy of solution or enthalpy of mixing [ 8 ]. The PS model proposed by Covington et al. [ 3 ] and adapted to the enthalpic effect analysis by Balk and Somsen [ 9 ] is based on the simplest version of the

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