Simple method for the determination of total fluorine in aqueous fluoroborate solution

Abstract

A method for the determination of total fluorine in aqueous fluoroborate solution without distillation of fluorine was investigated. In order to decompose fluoborate complex to fluoride ion several methods were tested. Fluoroborate was not fully hydrolyzed on heating on a water bath even in an alkaline solution, and did not decompose completely with only evaporation to dryness. Complete decomposition was accomplished by fusing a residue after evaporation to dryness.
Analytical method for total fluorine was established as follows: A 1 ml of sample solution containing 120 ppm fluorine was taken into a nickel crucible and 1 ml of 5% NaOH solution was added. The liquid was evaporated to dryness and then the residue was fused for a few minutes on a burner. After cooling 10 ml of an ionic strength adjustment buffer solution was added. The fluoride concentration was then measured by a fluoride sensitive electrode.
The method was rapid and simple, and was applicable to the total fluorine analysis of waste water in plating industry.