ABSTRACT
This chapter describes concepts, equations, and programs related to equilibrium calculations for multiligand complexes. Examples include the complexes of ferrous iron and 1,10-phenanthroline, o-Phen, and complexes of Zn(II) and Ni(II) with ammonia. After a brief discussion of the Fe(II)/o-Phen complexes, the chapter continues with some background information such as discussions of relationships among cumulative formation constants and equilibrium concentrations, fractions of complexes in different forms and distribution plots. After a brief discussion of approximation procedures the discussion continues with a description of the basis for a program to solve a charge balance equation for reactions associated with the formation of Fe(II)/o-Phen complexes. The chapter then continues with extensions of the charge-balance equation for the Fe(II)/o-Phen reaction to other reactions involving complexes with up to six ligands per metal ion. The discussion then continues with a description of a program to do calculations for complexes with up to six ligands per metal ion. The chapter continues with descriptions of selected applications of the iterative program, including calculations for the colorimetric determination of iron and predicting whether metal hydroxides will precipitate from solution. The chapter ends with comparisons of results calculated using approximate and iterative options.
