HypCal

Determination of stability constants and formation enthalpies from calorimetric data

For further details concerning the way the program works see P. Gans, A. Sabatini and A. Vacca, Simultaneous Calculation of Equilibrium Constants and Standard Formation Enthalpies from Calorimetric Data for Systems with Multiple equilibria in solution, J. Solution Chem., (2008) 37, 467-476. (requires Acrobat reader)

This program (updated from HypDH to HypCal) enables the calculation of

• either formation enthalpies using previously determined stability constants
• or formation enthalpies and stability constants

in systems where one or more complexes are in equilibrium in solution with a set of reagents. It is a Windows application. Key features are as follows

• There are no restrictions on the number of reagents or equilibria
• Typically HypCal uses calorimetric titration data; multiple titration curves can be treated simultaneously
• Data import may be from a file containing titre, corrected heat^* data pairs
• Batch data may also be used
• Data is imported from ASCII files containing titration volume, corrected heat data pairs
• Heats may be expressed in Joules or calories
• Stability constants may be fixed at "known" values, or refined
• Formation enththalpies may be fixed at "known" values, or refined
• Data may be fitted interactively on-screen before refinement
• Refinement is by a stabilised non-linear least-squares method with Jacobian calculated by means of analytical formulae
• Reaction entropy may be calculated

^* Corrected heat is the heat developed in a titration step, corrected for all non-chemical effects such as heat of dilution, calorimeter effects etc.

This example shows a system with three reagents and eight complexes Stability constants and reaction enthalpies for all complexes except ML, MLH and M₂L (M = MeHg⁺, L = gly^-) have been determined in separate experiments. The formation enthalpies are "live", that is, they change with every change of stability constant.

Stability Constants home page