The electromotive force E of the amalgam cell {LixHg1-x \ Li2SO4(m) \ Hg2SO4 \ Hg} has been measured as a function of the mole fraction x of Li metal in amalgams, and of the molality m of Li2SO4 in (methanol + water) and (acetonitrile + water) solvent mixtures containing up to 0.3 mass fraction of the organic component, at the temperature 298.15 K. The respective standard electromotive forces EO, have been determined together with the relevant activity coefficients gamma(+/-) as a function of Li2SO4 molality. A new scheme is introduced here and implemented for verification of the internal consistency of the gamma(+/-) results in terms of complementary pairs of concentration cells with transference. The E-m(o) depends linearly on the mass fraction w of the organic component of the solvent mixture within the range explored, according to:E-m(o)/V = 2.80137 - 0.20325w(methanol),E-m(o)/V = 2.80137 - 0.23139w(acetonitrile),which reproduce the observed E-m(o) values to within +/-0.2 mV.