Number: 2004-036-1-100
Title: Establishing recommended data on thermodynamic
properties of hydration for selected organic solutes
Task Group
Chairman: 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>
Objective:
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.
Description:
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.
