Phương trình Nernst của điện cực calomel là:

\[{\varepsilon _{cal}} = {\varepsilon ^0}_{cal} + \frac{{RT}}{{2F}}\lg \frac{{{{\left[ {Hg} \right]}^2}.{{\left[ {C{l^ - }} \right]}^2}}}{{\left[ {H{g_2}C{l_2}} \right]}}\]

\[{\varepsilon _{cal}} = {\varepsilon ^0}_{cal} + \frac{{RT}}{{2F}}\lg \frac{{\left[ {H{g_2}C{l_2}} \right]}}{{{{\left[ {Hg} \right]}^2}.{{\left[ {C{l^ - }} \right]}^2}}}\]

\[{\varepsilon _{cal}} = {\varepsilon ^0}_{cal} + \frac{{RT}}{{2F}}\lg \frac{{\left[ {Hg} \right].\left[ {C{l^ - }} \right]}}{{\left[ {H{g_2}C{l_2}} \right]}}\]

\[{\varepsilon _{cal}} = 0 + \frac{{RT}}{{2F}}\lg \frac{{\left[ {H{g_2}C{l_2}} \right]}}{{\left[ {Hg} \right].\left[ {C{l^ - }} \right]}}\]