SOLUBILITY OF SILVER IN LIQUID CESIUM AND THERMODYNAMIC PROPERTIES OF THESE SOLUTIONS

For a number of years, the Institute of High-Temperature Electrochemistry of the Ural Branch of the Russian Academy of Sciences has been determining the solubility of silver depending on temperature both in individual potassium and cesium, and with additions to these alkali metals of their halides. At the beginning of the study, they were assumed to be corrosive due to the prevailing opinion in the literature about the low solubility of silver in potassium and even less in cesium. In this work, it is shown that the solubility of silver in cesium is greater than in potassium. Here are measurements of the solubility of silver in liquid cesium at temperatures from 500 to 900°C. The average value of solubility for each temperature varied from 0.94 to 11.1 mol % Ag, respectively. Experimental data on the solubility of silver in cesium are approximated by a polynomial of the second degree. N_Ag = 6.066 · 10^–5T₂ – 5.966 · 10^–2T + 15.58, where N_Ag is silver solubility in mol %, Т is temperature in °C. In this article, using data on the solubility of silver in cesium and the ideal Schroeder solubility equation, the values of the activity coefficients of silver and the partial enthalpy of mixing of silver and its partial excess entropy in these solutions were obtained. They are respectively equal: \({{\overline {\Delta H} }_{{{\text{Ag}}}}}\) = 38 154.8 J/mol and \({{\overline {\Delta S} }_{{{\text{exAg}}}}}\) = 14.215 J/(mol · K). The Schroeder equation was used under the assumption that the enthalpy of silver melting is independent of temperature. The values of the logarithm of the silver activity coefficient versus temperature are approximated by the equation: ln(yAg) = 4589 · 1/T – 1.7097. Approximation error R² = 0.9818.