The interaction of magnesium ions with biomolecular species is fundamental to the regulation of many biological processes. A mathematical technique to investigate such interactions is described. The concept of a pseudo-formation curve is discussed and the relevance and applicability of such constructions to the study of solute-solute interactions is outlined. Analysis of curves based on the published variation of chemical shift data of various nuclei of adrenaline and dichloroisoprenaline in aqueous solution, in the presence of increasing concentration of the complex Mg-ATP, is described. Unambiguous indentification of specific interactions and the stability of the species produced is shown to be feasible. Some variation of the values of formation constants deriving from different nuclei reflects the significance of molecular environmental factors on the parameters used.