Limits of the application of calorimetry to the simultaneous determination of equilibrium constants and enthalpy changes of chemical reactions in solution

Abstract

A ‘trial and error’ procedure with use of calorimetric data for the determination of K, the dissociation constant, and ΔH of 1:1 complexes is examined and the limits of its application arising from propagation of errors are discussed.

A weighting procedure is suggested which takes into account the dependence of propagation of errors on the concentration of reagents and on their ratio.

Suggestions are made for the recognition of the presence of systematic errors; we emphasise that a good fit between calculated and experimental data can be compatible with fictitious values of K and ΔH if the experiments are conducted with constant concentration of one of the reagents.