Biamperometric end-point determination in the titration of fluoride with thorium nitrate

Abstract

The possibilities of the biamperometric end-point detection in the titration of fluoride by means of thorium nitrate are investigated applying different pairs of identical indicator electrodes. In unbuffered solutions using aluminium, bismuth and tin pairs of polarised indicator electrodes, amounts of 6.2-12.5 mg of potassium fluoride have been determined with an average deviation of less than 0.3%. In solutions containing buffer pH 3.0, polarised or nonpolarised pairs of aluminium electrodes can be applied only. Amounts of 5.2-10.5 mg of potassium fluoride and 3.0 mg of sodium silicofluoride have been determined with an average deviation of less than 0.8%. In all determinations the content of ethanol was 75% at the end-point of the titration. The results obtained are in a good agreement with those of potentiometric, photometric and amperometric titrations. © 1974 Springer-Verlag.