Water vapour partial pressures and water activities in potassium and sodium hydroxide solutions over wide concentration and temperature ranges

On the basis of previously published experimental data, corresponding correlation equations have been derived for the water vapour partial pressure over potassium and sodium hydroxide solutions over wide molality and temperature ranges (mKOH = 0–18 mol kg−1, mNaOH = 0–25 mol kg−1; t = 0–300°C). The correlation equations can be exploited for various scientific and technical purposes, e.g. for computing the water vapour content in gases developing during the conventional and advanced water electrolysis from concentrated KOH solutions at elevated temperature and pressure. Similar correlation equations have also been derived for water activities in potassium and sodium hydroxide solutions for the same molality range of the two hydroxides as specified above and for temperatures between 0 and 200°C.