Determination of fluoride in steelworks materials with a fluoride ion-selective electrode

Abstract

A method has been developed for the determination of fluoride in ores, slags, mould dressings, fluorspars, etc., covering the range 0.02–50% of fluoride. Samples are fused in a boric acid-sodium carbonate mixture and, after extraction with aluminium chloride-hydrochloric acid solution, a sodium 5-sulphosalicylate buffer is added. The fluoride concentration is then measured by means of a fluoride ion-selective electrode. Complete dissolution of the samples ensures a total fluoride determination and the procedure avoids the conventional perchloric acid distillation technique. The method is free from interferences by boron and most of the elements that are normally encountered in slags, etc. A standard deviation of 0.03% at the 1.70% fluoride level has been obtained.