X-ray studies of concentrated aqueous solutions

Abstract

Concentrated aqueous solutions of three transition metal bromides (ZnBr2, CuBr2, and NiBr2) and an alkali bromide (RbBr) have been studied with differential anomalous scattering (DAS) and extended x-ray absorption fine structure (EXAFS). The aq-ZnBr2 solutions exhibit considerable inner-shell ion complexing with the formation of tetrahedral complexes about the Zn2+. In aq-CuBr2, the Cu2+ has an octahedral coordination shell. Most of the anions are bound directly to the cations in both solutions. In contrast, there are only a few Ni-Br nearest neighbors in aq-NiBr2. Instead, cations and anions share hydrating water molecules. Preliminary data show that any ion complexing in aq-RbBr must be weak. These results are in good agreement with published thermodynamic studies. © 1987 American Institute of Physics.