A structural study of the aqua-anions NO3-, BrO3- and ClO3- by difference methods of X-ray diffraction

The method of X-ray diffraction with isomorphic substitution has been extended to aqueous solutions containing complex ions. In a study of isomorphism between NO3-(aq), BrO3-(aq) and ClO3-(aq), it is found that the NO3- and BrO3- ions are isomorphic up to the level of the first-order difference indicating a similarity in their anion-hydration structure. Based on the isomorphism of these two ions, and because the water molecules are only weakly perturbed from their structure in pure water, a second-order difference calculation was made and the ion-ion pair correlation function of these two ions obtained. The results show that the most probable ion-ion separation is between 5 AA and 11 AA and the distance of closest approach is 4.8 AA. NO3- and BrO3- are found, however, not to be isomorphic with ClO3-.