Concentrated aqueous solutions and liquid hydrates of zinc chloride: a study of their solvent behaviour using intershell, charge-transfer, and d–d absorption spectra
Abstract
The u.v.–visible absorption spectra of TI+, Pb2+, Co2+, Ni2+, VO2+, and Fe3+ were examined in the ZnCl2–H2O system, with salt: water ratios ranging from 1:3 to 1:108. The spectral trends were compared with those in the CaCl2–H2O system, and they indicated that at low water contents, including compositions corresponding to the liquid salt hydrates, the two systems differ markedly. Whereas the CaCl2-H2O system furnishes a high concentration of Cl– ions but very little water for co-ordination with solute metal ions, the ZnCl2-H2O system, in marked contrast, appears to contain water but virtually no ‘free’ chloride ions, any chloride co-ordinating to solute metal ions being in the form of part of a chlorozincate group.