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Current Project

Physical and Biophysical Chemistry Division (I)


Number: 2004-036-1-100

Title: Establishing recommended data on thermodynamic properties of hydration for selected organic solutes

Task Group
: Vladimir Majer

Members: V. Dohnal, R. Fernandez-Prini, M. Frenkel, A.H. Harvey, J. Sedlbauer, and E.L. Shock

Remark: This project is co-funded by the International Association for Properties of Water and Steam (IAPWS) <www.iapws.org>

The objective of the project is to establish a database of thermodynamic properties of hydration for approximately 200 selected organic solutes at reference condition of 298.15 K and 0.1 MPa and as a function of temperature and pressure up to the near critical region of water. The values of hydration properties for solutes covering different molecular structures will be calculated from the reliable experimental data for aqueous and pure solutes. The established database will be used as a standard for testing and establishment of new physico-chemical models and methods of molecular simulation as well as for developing semi-theoretical prediction schemes of interest for chemical engineering, environmental chemistry and geochemistry.

Thermodynamic properties of hydration (TPH) covered in the project are: the Gibbs energy of hydration and its temperature and pressure derivatives (the enthalpy of hydration, the heat capacity of hydration and the partial molar volume at infinite dilution), other TPH result from their combinations; for exact definitions and inter-relationship see Appendix 1 (pdf).

TPH express the difference between the property of a solute in the standard state of infinite dilution at a given temperature and pressure and that of an ideal gas at the same temperature and reference pressure of 0.1 MPa. Thus they characterise the transfer of a solute from a state where molecules are not interacting to the state where the solute molecules interact solely with the water solvent. Due to this definition they can be used conveniently in testing and conception of theoretical models and simulation approaches for dilute aqueous solutions developed by physical chemists. At the same time, TPH allow an easy calculation of partition coefficients (such as the Henry's law constant, air-water partition coefficient, relative volatility, etc.) and of the thermodynamic reaction constants for aqueous systems. Therefore they also have a practical value of interest for chemical engineers and environmental chemists. In addition, the high temperature / high pressure TPH are required to characterize phase and chemical equilibria in hydrothermal systems and to guide the development of geochemical prediction schemes for aqueous fluids.

TPH cannot be directly measured but are calculated from the experimental data characterising aqueous and pure solutes, which result from phase equilibrium, calorimetric and volumetric measurements. Appendix 1 (pdf) summarises equations used to calculate TPH and lists types of experimental data that can be exploited.

The task group will select from the primary literature the best available experimental results for establishing a database of reliable values of TPH for 100 - 200 organic solutes and several common gases. In selecting the solutes, three main criteria will be observed:

i) coverage of the widest range of molecular structures, indispensable for the development of theoretical models and group contribution prediction schemes,
ii) availability of reliable experimental data, particularly with regard to the HT/HP region,
iii) technological and environmental importance of individual solutes.

The database will comprise values at the reference condition for about 200 solutes and at elevated temperatures (T < 673 K) and pressures (p < 40 MPa) for about 100 solutes. For several solutes the recommended TPH will be given up to the critical region of water where they undergo remarkable changes. A tentative list of the classes of solutes covered and their respective numbers are given in Appendix 2 (pdf). Every effort will be made to supply a database which will not be biased by use of any particular correlation model for interpolating or extrapolating the data. This project requires collaboration of researchers having complementary knowledge in data evaluation and in different experimental techniques used for obtaining data for aqueous and pure solutes.


Last update: 8 February 2005

<project announcement to be published in Chem. Int.>


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