The standard potential of the silver-silver bromide electrode and ion solvation in t-butyl alcohol + water mixtures at 298.15 K

E.m.f. measurements of the cell ���������������������� Pt|H2|HBr(m), ButOH(X), water|AgBr|Ag have been made at 298.15 K for solvent compositions X = 10, 20, 30, 40, 50 and 70% (w/w) of t-butyl alcohol. These have been used to evaluate the standard potential of the silver-silver bromide electrode and the free energy of transfer, ΔG�t, of the acid from water to the respective solvent media. These ΔG�t values, along with those for hydrochloric acid, are briefly discussed in relation to ion solvation. ��� Mean ionic activity coefficients of hydrobromic acid in the various solvents have also been calculated.