The hydration structure around chloride ions in aqueous solution

Abstract

The hydration structure around chloride ions has been determined for several heavy water electrolyte solutions at various concentrations by the first-order difference method of neutron diffraction. Particular attention has been focused on aqueous zinc chloride solutions, for which results are now available. The following conclusions have been drawn from these data: (1) the chloride-water radial distribution function has a similar form in all solutions studied and is consistent with a well defined hydration geometry, with the Cl—D nearest neighbour distance, r_CID, in the range 2.2 < r_CID/Å < 2.3 and a nearly linear Cl—D—O arrangement; (2) the number of water molecules in the first coordination shell of Cl^–(the hydration number, n_D) is ≲6 and depends on both the ionic strength and the type of cation.