|Start:||01 January 2000|
|End:||17 December 2005|
To facilitate the calculation of reliable stability constants for applications in an assortment of natural media (e.g. seawater, biological fluids).
To do this reliable activity coefficients must be available. This will be accomplished by preparing a computer based method for correcting stability constants for ionic strength changes in the range 0 - 5 mol dm-3 (with routines for converting to molal) using activity coefficients calculated from the Pitzer equation and Specific Interaction Theory (SIT). A database of published coefficients will be prepared and, where values are not available, they will be calculated using SIT approximations. The software will be made freely available on the web. It will not contain a critical evaluation of existing parameters.
Semi-empirical methods that have been used to model complexation reactions include the Pitzer models and Specific Ion Interaction Theory (SIT), and these have been shown to be equivalent for all practical purposes (I. Grenthe and A. Plyasunov, Pure Appl. Chem., 69, 951-8, 1997). Both depend on selecting and applying interaction coefficients and parameters applicable to the system being modeled.
Compilations of recommended values for many common ions, and possible approximations for calculating unknown values, have been published. However a worker wishing to apply corrections in a particular system can be faced with time-consuming research. The proposal is that a computer-based method of calculating activity coefficients (and hence stability constants corrections) is developed. This will contain a database of parameters for systems that have been studied, together with a subroutine for calculating values for which recommended values are not available. The database will not be a critical evaluation of literature values but will be designed to allow new values to be added (or existing values corrected) by the user as necessary.
The format of the program will facilitate linking to speciation software to allow modeling under a range of ionic strengths and conditions.
Version 1.2, released in Sep 2002, includes improved graph drawing routines and the list of SIT parameters have been extended to include those for many carboxylic acids. For a review of SIT, read about it in Chem. Int. Nov 2002
Version 1.5 was released in September 2003
- for Windowns 9x, NT, 2000, and XP, download the following package > SIT-v1.5-Sep03.zip (zip file - 445KB)
- for a Russian version, download the following package > SIT-v1.5-Sep03_Russian.zip (zip file - 495KB)
For a review, read about it in Chem. Int. Nov 2003
> Nov 2004 report update (pdf file - 12KB)
A suite of inter-linked programs -‘The Adjustment, Estimation and Uses of Equilibrium Constants in Aqueous Solution’- has been developped and includes:
> download the entire suite > Aq_Solutions.zip (zip file - 6.97MB)
The current version of the suite of programs may also be downloaded from: public.kubsu.ru/aquasolsoft/ and select 'Projects'
> see related project 2006-010-1-500 titled 'Adjustment, estimation and uses of equilibrium reaction constants in aqueous solution'