The activity of the components of a Na-K-Cs system at high temperatures

The activity coefficients of the components of a Na-K-Cs ternary system in a temperature range of 773-1200 K are determined using the previously calculated thermodynamic properties, in particular, the activity of the components of binary alloys of alkali metals such as Na-K, Na-Cs, and K-Cs, at high temperatures [1-3]. The sides of the triangle of the phase diagram of this system are constituted by the binary Na-K, Na-Cs, and K-Cs binary alloys. The results obtained are used to calculate the saturated vapor pressure of the sodium-potassium-cesium eutectic (22.1 wt % K and 73.8 wt % Cs [4, 5]) in the same temperature range. The calculated data are in good agreement with the recommended reference data [6].