EFFECT OF ACETATE BUFFER ON POTENTIOMETRIC TITRATION OF FLUORIDE WITH LANTHANUM USING A LANTHANUM FLUORIDE MEMBRANE ELECTRODE

Precipitation titrations of fluoride with lanthanum nitrate using a lanthanum fluoride electrode have been carried out at constant ionic strength and different acetate concentrations. The titration curves have been analysed by rigorous equilibrium calculations with the computer program HALTAFALL. Acetate ions have been shown to enter the solid phase, forming precipitates with the formula LaF3-xAcx (0<x<1). The presence of acetate causes the electrode to work sluggishly and to deviate from the Nernst law. These effects increase with increasing acetate concentrations and may possibly even occur at high nitrate concentrations. © 1969.