The Hydration of Tungstate and Molybdate Ions in Aqueous Solution

The structure in aqueous solution of the hydrated tungstade and molybdate ions WO 4 2- and MoO 4 2- has been derived from large angle X-ray scattering measurements using MoO 4 2- as an isomorphous substituent for WO 4 2- The W(Mo)-O bond lengths are 1.78 6 Å and do not differ from those found in crystal structures. A fairly well-defined hydration shell of about 12 water molecules surrounds the XO 4 2- ions at a W(Mo)-H 2 O distance of 4.06 Å.