Association constants for the NaSO4- ion pair in concentrated cesium chloride solutions

Values of the association constant, beta(NaSO4-), for the weak ion-pair for med by sodium and sulfate ions in aqueous solution have been determined at 25 degrees C by high precision sodium ion-selective electrode potentiometry in solutions of ionic strength ranging from 0.50 to 7.00 M in CsCl media a nd in 1.00 M Me4NCl. The data in CsCl media were fitted to an extended form of the Debye-Huckel equation which yielded log beta(NaSO4-)(0) = 0.834 +/- 0.005 at infinite dilution. Evidence is also presented for the formation o f very weak ion-pairs between Cs+ and SO42-. (C) 1999 Elsevier Science B.V. All rights reserved.