Verified analysis of hydration of electrolytes

Rigorous thermodynamic analysis of hydration parameters has been fulfilled. Water solutions of potassium chloride were studied in a wide range of concentrations from 0 to 23 wt.% in the temperature range 283.15–308.15 K by ultrasonic and densimetry measurements using heat capacity data at constant pressure. The structural characteristics of hydrated complexes are analyzed: hydration number, volume of the stoichiometric mixture of K⁺ and Cl^? ions without hydration shells, compressibility and molar volume of water in hydration spheres, and their concentration and temperature dependences. The mean pressure in the hydration spheres of KCl ions is shown to be about 350 atm at 298.15 K.