Lanthanum Fluoride Electrode Response in Water and in 1M Sodium Chloride

摘要

Response of the fluoride-selective electrode in water and 1M NaCl solutions is accurately predicted by the Nernst equation for fluoride activities from 0.1 to 0.000001M when liquid junction potential changes are minimized. Useful response is available above 0.1M and can be obtained with difficulty down to 2 parts per billion. Activity coefficient data for fluoride in solutions of total ionic strength between 0.0001 and 0.1M are validated, and a simple method for measuring fluoride impurity levels in other substances is described. There is no detectable chloride interference with electrode response in 1M NaCl for fluoride concentrations down to 0.0001 and 0.1M. (Author)