AN X-RAY-DIFFRACTION STUDY OF PREFERENTIAL SOLVATION OF IONS IN MGCL2-WATER-METHANOL TERNARY-SYSTEMS

Results of X-ray diffraction experiments are presented on concentrated MgCl2-water-methanol ternary systems. Detailed structural analysis of the solutions has been carried out in order to determine the average structure of the first coordination shells of the ions. The main struc tural parameters are in agreement with the reference aqueous and metha nolic solutions studied previously. Both the Mg2+ and the Cl- ions are surrounded by 6 solvating molecules in average in each solution, and the distance between the ions and their first solvating neighbors does not vary with the composition. The average ratio of the water molecul es to the methanol molecules within the first neighbor shell correspon ds to the stoichiometry of the solutions, and thus no direct proof for significant extent of preferential solvation can be presented by the X-ray diffraction method in the studied systems.