Pyrohydrolysis for the rapid determination of small and large amounts of fluorine in fluorides, silicate minerals and rocks using an ion-selective electrode

Abstract

A simple and rapid method for the determination of fluoride in the range above 10ppm up to 48.67 wt.% for CaF₂ within a total time of 15 minutes is described. Samples are mixed with PbO₂ in the ratio 1 : 3; and the fluoride is liberated in an induction furnace within ca. 10 minutes. The fluoride is collected in a 0.025 molar sodium-hydroxide solution and after adding 100ml buffer (1M sodium citrate, 1M sodium chloride), the solution is filled up to 250ml with distilled water, and measured by an ion-selective electrode using the technique of standard addition. Analyses of five international reference samples show excellent accuracy from 0.5 to 3% with a standard deviation of less than 4% (e.g., for a fluoride contents of 442ppm in Andesite AGV-1).