A new computer-based method for determining ΔH from digitized spectra: the nickel(II)+ chloride system in dimethyl sulphoxide

Abstract

A new method is described for calculating equilibrium quotients and enthalpy values from digitized spectra, for two-species equilibria, based on the concept of internal linearity. The method is evaluated by comparing the results obtained with those reported earlier¹ for the system nickel(II)+ chloride in dimethyl sulphoxide : the results agree well. Fourth-derivative curves of the digitized spectra are computed and permit definitive identification of the species present in solution at any one time, and hence the temperature range over which the two-species equilibrium [NiCl₂(dmso)₄]⁰+ Cl^–⇌[NiCl₃(dmso)]^– occurs can be precisely determined. The derivation of the relationship between ΔH and β, the internal linearity constant, and the computing principles employed, are given in the Appendix.