Project Details Critical Evaluation of Thermodynamic Data of Sulfate Complexes in Solution

Project No.:
Start Date:
01 April 2012
End Date:
30 August 2019
Division Name:
Analytical Chemistry Division
Division No.:


This project aims to compile and critically review the thermodynamic data (stability constants, enthalpies and entropies) available in the scientific literature on metal ion- sulfate complexes in aqueous solution.

Such complexes are important in environmental chemistry, hydrometallurgy and geochemistry. Sulfate is a major ionic constituent of natural waters, including many geological brines, and binds significantly with most metal ions. Sulfate hydrometallurgy is widely used in the extraction and purification of a number of economically-important metals.

This project will provide reliable thermodynamic data for use in chemical speciation modeling in many fields of pure and applied chemistry.


This project involves the comprehensive compilation, from the literature, of experimental thermodynamic data (stability constants, enthalpies and entropies) pertaining to metal ion-sulfate complexes in aqueous solutions. The compiled data will be critically reviewed and specific recommendations made as to their reliability.

Data compilation will be based on the “Stability Constant Handbook” (Chem. Soc. and IUPAC), which give a comprehensive coverage of the older literature, and the IUPAC SC-Database for more recent data. These sources will be cross-checked against other databases (eg, JESS) and supplemented by cross-referencing and literature searching via Chemistry Abstracts.

Critical evaluation will employ the methods established (by SSED and former Commission V.6) in previous IUPAC work of a similar nature.

The project will be incorporated into the activities of the SSED. Sub-sections of the work will be distributed to recognized experts in the area for comment.

To the best of our knowledge, no previous comprehensive critical evaluation of metal ion-sulfate data has been published. However, an almost completed IUPAC project Chemical speciation of environmentally significant metals with inorganic ligands (project 1999-050-1-500) has included five metal-sulfate systems. These systems will not be re-evaluated unless significant new information is found; instead a summary of the findings of that project will be incorporated into the Technical Report.

The literature in this area is widespread, frequently contradictory and often impenetrable to the non-expert.


Update July 2016 – Over one thousand references have been obtained to date and are being examined in detail to assess their quantitative content (stability constants, enthalpies, entropies and related data). At least another one hundred references are on order, mostly difficult-to-obtain material from less-common sources. The data are being compiled into appropriate tables so that a critical evaluation of all the published results can be made. Progress on this aspect of the project is slow due to the other commitments of the participants.

The participants are in regular contact by email and have been meeting in person once a year for brief periods in Warsaw and, where possible, at the regular (yearly) meetings of the IUPAC Sub-Committee on Equilibrium Data (SSED).

Dr Guminsky is presenting a talk on the project at the 17th International Symposium on Solubility Phenomena, being held in Geneva, Switzerland, 24-29 July, 2016. It is anticipated further presentations will be made at other international conferences as the work heads towards its completion.

Last update 8 July 2016