ISO 5439:1978

Acid-grade fluorspar — Determination of available fluorine content — Potentiometric method after distillation

Specifies a potentiometric method using a fluoride-ion sensitive electrode. After destillation of fluorine from the test portion in the presence of perchloric acid the distillate shall be titrated with lanthane nitrate solution. Applicable to products having a calcium fluoride content greater than 90 %.