The electromotive forces at 15°, 25° and 35° of the cells H₂ | HCl (m) | AgCl - Ag in alcohol and alcohol-water mixtures have been measured and the affect of change in the nature of the solvent studied. From the measurements have been calculated: - (1) The activity coefficientsof the acid in the solutions, and the activity coefficients in ideal solutions referred to the ideal water solution as unity. (2) The change in free energy and heat content attending the cell reaction 1/2H₂ + AgC1 - Ag + HCl at various concentrations. (3) The change in free energy and heat content attending the transfer of one mol of HCl from concentration m to the ideal solution. (4) The change in free energy and heat content attending the transfer from the ideal alcoholic solutions to the ideal water solution. The nature of the results gives strong support to the general idea of hydration of ions.