Project Details Adjustment, estimation and uses of equilibrium reaction constants in aqueous solution

Project No.:
Start Date:
01 July 2006
End Date:
01 November 2008


To prepare (and improve) programs to treat quantitatively the dependence of activity coefficients (and hence equilibrium constants) on ionic strength and on the presence of dissolved gases.To explore and test computer-based ways of displaying these effects graphically and the influence they will have on species distribution curves.


A previous IUPAC project (# 2000-003-1-500) has produced a suite of programs to study quantitatively the influence of ionic strength changes on equilibrium constants, with particular emphasis on using Specific Interaction Theory (SIT). In this project we propose to extend this work in the following ways:

  • To apply Pitzer parameters in a more general way to equilibria of environmental and industrial importance. Particular importance will be given to sea water and mixed fluids.
  • To extend and improve a database of published SIT and Pitzer-related parameters. This database may be accessed by all relevant programs in the suite and may be edited by the user.
  • Currently the package allows calculations on the effects of dissolved O2. This will be extended to cover other environmentally important gases (e.g. air, H2, N2, rare gases, N2O, CH4, and other paraffins
  • To explore and test ways of displaying graphically the relationship between ionic strength and temperature with activity coefficients, lg Kº and lg K;
  • To explore and test ways of displaying graphically the effects of errors on the relationships studied above.
  • To calculate, and demonstrate graphically, the effect of errors on species distribution curves.
  • To prepare a database of reliable literature values of the dependence of stability constants on temperature.

The current version of the suite of programs ( about 7 MB) is available from project # 2000-003-1-500


> July 2007 report update (pdf file – 10KB)

> download the entire suite > Aq_solutions_Nov2008 (zip file – 7MB)

project completed

* project announcement published in Chem. Int. Sep-Oct 2006