Spectrographic method of investigation of complexing equilibria of whole series of rare earths and some other elements

A variant of spectrographic method, permitting to conduct quantitative investigation of complexing equilibria for the whole series of rare earths and cetain other elements, stability of the complexes of which is close to rare earth complexes, has been developed. The method essence is in preliminary spectrographic study of complexing in the double system Nd-L (Eu-L or Er-L), where L is any colo less ligand, as a result of which equilibrium concentrations in the range of existence of all the complexes, their stability are determined, as well as concentration of unbonded ligand (Csub(free)), and then in the plotting of graphic dependence of equilibrium concentration of aquo ion [Nd3+) on Csub(free). Then the ternary system Nd-L-M is studied, where M is any other lanthanide or any suitable metal ion under conditions, when a certain complex is formed, which is selected for the study according to preliminary study of the double system Nd-L. According to Nd absorption spectra the equilibrium concentration of aquo ion and neodymium complex with ligand in the presence of the second metal ion is determined. On the basis of the value of [Nd3+] equilibrium concentration in the ternary system, determined spectro-graphically, and according to the diagram of [Nd3+]-Csub(free) dependence in the double system, the concentration of Csub(free) in the ternary system is found