Ionic strength dependence of formation constants-X: proton activity coefficients at various temperatures and ionic strengths and their use in the study of complex equilibria

The activity coefficients of the proton were determined in aqueous solution in the presence of several background electrolytes at 10, 25, 37 and 45 degrees and 0.01 < or = I < or = 1M. The results indicate that the proton activity coefficients are fairly independent of the different salts used as background, in particular when ion-pair formation between cations and anions of the medium is taken into account. This result is in agreement with the findings of previous works in this series. Some previously published data were reanalysed for comparison, and showed excellent accordance with the present results. A general equation for calculating proton activity coefficients is reported.