Experimental investigation of the activity of sodium in a liquid sodium–potassium alloy in a wide temperature range

The EMF method is applied to investigate the activity of sodium in a molten sodium – potassium alloy containing $87.2$ wt. $\%$ of potassium. The measurements are performed in two different experimental setups. One of them uses glass containing sodium ions as electrolyte, and the other one uses beta-ceramics. Therefore, the limiting experimental temperature in the first case does not exceed $550$ K, while in the second case, it is about $750$ K. The maximal relative error of the experimental data on the activity of sodium in a liquid $\mathrm{Na}$–$\mathrm{K}$ alloy is approximately $3\%$. The discrepancy between the measurement results and the experimental and theoretical data available in the literature is within this error.