On complexing in the MI-CdI2-H2O (M=Li, Cs) systems from Ksub(α), Cd line chemical shift data

Studied is the cadmium complex formation in MI-CdI2-H2O (M=Li,Cs) systems by the method of chemical shift measuring (CS) of Ksub(α1)-cadmium line. Solutions were investigated in a wide range of concentrations, given by the r(r=[I]/[Cd]) parameter in the vicinity solubility isoterms of the given salt systems. Three regions may be singled out on the XC(r) dependence curves:0 < r <= 4; 4 < r < 8; r >= 8. In the first region the formation of cadmium aqua complexes takes plase. In the 4 < r < 8 region individuality appears in the behaviour of systems. In the LiI-CdI2-H2O system the [CdI4]2- complex form becomes dominating already at r approximately 4, and in the CsI-CdI2-H2O system it dominates at r >=8. It is supposed that in the system with CsI at 4 < r < 8 more highly coordinated complexes exist, namely [CdI5]3- and [CdI6]4-