ISO 4284:1993

Acid-grade and ceramic-grade fluorspar — Determination of sulfide content — Iodometric method

The principle of the method specified is digestion of a test portion in a sealed apparatus in a mixture of hydrochloric acid, tin(II) chloride and boric acid solutions, absorption of the liberated hydrogen sulfide, entrained in a stream of oxygen-free argon or nitrogen, in zinc acetate solution and iodometric determination of the zinc sulfide formed. The method is applicable to products having a sulfide content equal to or greater than 0,001 % (m/m). It is not applicable, if presence of polysulfides is suspected.