X-RAY DIFFRACTION DETERMINATION OF THE STRUCTURE OF THE ION NEAREST ENVIRONMENT IN AQUEOUS SOLUTIONS OF MAGNESIUM CHLORIDE AND NITRATE

Quantitative characteristics of the nearest environment of ions in aqueous solutions of magnesium chloride and nitrate are determined by single crystal X-ray diffraction in a wide concentration range. It is found that in magnesium nitrate solutions, the nearest environment of the cation consists of six water molecules in the entire concentration range. A similar characteristic of the cation coordination sphere is also observed in 1:40 and 1:80 magnesium chloride solutions. The distinction between solutions with different anions is that in the saturated and 1:20 solutions of magnesium chloride, an insignificant amount of ions forms contact ionic pairs in which the nearest environment of the Mg2+ ion consists of five water molecules and one chlorine ion. When the solution is diluted, the chloride ion leaves the first coordination sphere of the cation and it becomes a regular octahedron consisting of six water molecules.