Small angle neutron scattering and structural properties in electrolytic solutions

A new direct indication concerning the structural properties of liquid systems is obtained for the first time. Small angle neutron scattering (SANS) measurements have been performed on solutions of ZnCl₂, NiCl₂, CuBr₂ in D₂O and in non aqueous solvent (EtOAc). The spectra, taken at room temperature, as a function of concentration, in the range $\text{0.019 ? K ? 0.25 (}\text{A}\text{?}{}^{\mathrm{?1}}\text{)}$ show in aqueous solvent an “abnormal” k-dependent small angle coherent cross section. This anomalous contribution clearly indicates the existence in the systems of correlated regions (～ 30 Å) perhaps connected through a preferred distance of ～ 50 Å. Also in pure water the results seem to indicate the existence of correlated regions of finite size.