The ionization of water in NaCl media to 300°C

The apparent ionization quotient for water has been measured potentiometrically near the saturation pressure from 25 to 295°C in 1 and 3m NaCl using a previously described hydrogen-electrode concentration cell. The results are presented in terms of a modification of the Brönsted-Guggenheim treatment for activity coefficients of ions. The mathematical form of the temperature dependence for the interaction coefficients was indicated by the more extensive data on \(\gamma _{{\rm H}^ + } \gamma _{{\rm O}{\rm H}^ - } \) in KCl media. From a least-squares analysis of these data in NaCl along with the very precise data from the literature for NaCl media from 0 to 50°C, the following expression for the effect of salt concentration and temperature on logQ _w ^′ is obtained $$\begin{gathered} log Q'_W = log K_W + 2.0AI^{1/2} /(1 + I^{1/2} ) - p_1 + p_2 /T + p_3 T^2 + p_4 F(I)]I \hfill \\ - 0.0157\phi m_{NaCl} \hfill \\ F(I) = 1 - (1 + 2I^{1/2} - 2I) exp( - 2I^{1/2} )]/4I \hfill \\ \end{gathered} $$