In the deposition of ZnS by chemical bath methods (CBD) at basic pH it is common to see improved deposition in the presence of a second ligand. These ternary systems (three components; two ligands one metal) are usually modelled by considering only the formation of binary species. This short paper outlines a strategy for considering the incorporation of ternary species in defining the complexes formed in solutions used for deposition. It appears that solutions which deposit ZnS are not necessarily supersaturated with respect to hydroxy-species. The relationship of these methods to deposition from acidic baths is also briefly discussed.