Potentiometric investigation of the weak association of sodium and oxalate ions in aqueous solutions at 25°C

Tromans, A., Hefter, G. and May, P.M. (2005) Potentiometric investigation of the weak association of sodium and oxalate ions in aqueous solutions at 25°C. Australian Journal of Chemistry, 58 (3). pp. 213-217.

Abstract

The formation constant β(NaOx-) of the extremely weak ion pair formed between sodium (Na+) and oxalate (Ox2-) ions in aqueous solutions has been determined at 25°C as a function of ionic strength in tetramethylammonium chloride by Na+ ion-selective electrode potentiometry. The effects of trace Na+ impurities from all reagents were accounted for. An extrapolated value for β° of 6.6 ± 0.5 M-1 was obtained at infinite dilution, which is in good agreement with literature values. Attempts to measure this constant in 1 M CsCl media gave a β(NaOx-) value of 0.00 ± 0.06 M -1, probably because of competition between Cs+ and Na+ for Ox2-.