The structure of Cl⁻in aqueous solution: an experimental determination of gClH(r) and gClO(r)

The first and second isotopic difference methods of neutron diffraction have been applied to solutions of 2 molal NiCl 2 in H 2 O and 1.8 molal NiCl 2 in D 2 O. The results were used to obtain the radial pair distribution functions g ClH (r) and g ClO (r). Analysis of these functions shows that Cl - is coordinated to 6.4(3) water molecules at near-neighbour Cl-H(1), Cl-O and Cl-H(2) distances of 2.28(3) AA, 3.1(1) AA and 3.7(1) AA respectively. The data transcend those obtained in previous studies, which were carried out only at the level of the first difference, and so provide a sharper test of theoretical results obtained from computer simulation or integral equations.