Spectrophotometric determination of association constant of lanthanum salicylate

Abstract

Spectrophotometric evidence has been obtained for the formation of the ion-pair LaHSal²⁺ in aqueous solution of lanthanum salicylate. A new spectrophotometric method of determining association constants of ion-pairs of metal ions with anions of weak acids is described. The method, which dispenses with pH-measurements, has been applied to determine the association constant K={LaHSal²⁺}/{La³⁺}{HSal^–} for the LaHSal²⁺ ion-pair; at 25°C its value is 1.19 × 10².