Abstract A method is described for determining the concentration of fluoride in coal.
Coal ash is fused with sodium hydroxide, and the resulting melt is leached with distilled water.
This solution is diluted with an ammonium citrate buffer to produce a final solution having a pH in the range of 5.5 to 7.0. The fluoride concentration then is determined by measurement of the potential produced by a fluoride ion-selective electrode. The precision of the method is approximately 6-percent relative standard deviation. The quality of each chemical reagent is reagent grade or better. The pH of this solution is 4.7 to 4.9.