Values of the e.m.f. for the cell without liquid junction: Pt\H-2 (p = 101.325 kPa)\HCl(m(A)), GaCl3(m(B)), H2O\AgCl\Ag, are reported at five different temperatures from 278.15 K to 318.15 K. The standard association constants K of the ion pair [GaCl](2+) were determined by a linear extrapolation on the basis of the extended Debye-Huckel equation. The thermodynamic quantities for the ion association process were calculated, and the association entropy was found to be the main driving force in the process.