The sulphate ion in aqueous solution: an X-ray diffraction study of a ZnSO₄ solution

Two distinct X-ray diffraction studies of ~2 mol dm^-3 ZnSO₄ solutions were carried out in order to assess the possibility of studying the state of the sulfate ion in water and to verify whether and how structural information depends on possible differences in experimental data. It is shown that the X-ray diffraction method is unable to provide results capable of unambiguous modelling of the SO^2-₄ coordination; even the complete omission of sulfate-water interactions does not lead to unsatisfactory synthetic structure functions. This conclusion does not seem to be affected by differences in the experimental data; however, some characteristics of the `best' models can be affected by differences in experimental data that are within the limits of experimental uncertainties.