The second difference method of neutron diffraction and isotopic substitution was used to determine the pair radial distribution function g(ClCl)(r) in an 8.6 molal solution of lithium chloride in heavy water. The number of direct contacts between the Cl- ions was found to be 1.2 +/- 0.5. This observation is in marked contrast to that found in an equivalently concentrated nickel (II) chloride solution (8.6 molal Cl-), where no direct Cl-... Cl- contacts are found. (C) 2000 American Institute of Physics. [S0021- 9606(00)51609-2].