Hydration in concentrated aqueous solution

Abstract

Neutron diffraction experiments were carried out on aqueous solutions of lithium chloride in heavy water at three concentrations - 14, 3.6 and 1 molal. The first-order isotopic difference method was applied to the lithium ions, and structural results were obtained for the hydration: the Li - O and Li - D near-neighbour distances in the first hydration shell remain the same at 1.95(3) and 2.5(5) Å over the concentration range studied. However, there is an increase in coordination number from 3.2 at 14 molal to at 1 molal. There is also evidence for a relatively weak second hydration shell, which becomes displaced to larger distances at lower concentrations.