Transference Numbers of Concentrated Electrolytes and Characterization of Salt Bridges in the Ethanol + Water Solvent Mixtures

Emf. measurements have been made using the transference cells: Ag|AgCl|MCl (m2)|MCl (m1)|AgCl|Ag and M(Hg)|MCl (m1)|MCl (m2)|M(Hg) (where M = Na, K, and Cs and M(Hg) denotes a flowing M-amalgam electrode) at various molalities m2 > m1 of MCl salts in ethanol (1) + water (2) with ethanol mass fraction w1 up to 0.8. The results indicate that the ions in CsCl have approx. equal transference no. from pure water up to w1 = 0.6 for ethanol, but at w1 = 0.7 the transference nos. of the ions start to differ. Also, the transference nos. of the ions in KCl in ethanol + water approach 0.5, but at w1 > 0.4, the KCl soly. becomes insufficient for a salt bridge function. NaCl, which is not good as a salt bridge in water, is more useful with increasing ethanol concns., and the transference nos. of the ions approach 0.5 at ethanol mass fraction w1 > 0.8