Applicable to products having a total content up to 1 %. Is not applicable in the presence of zirconium or titanium. More than 0.006 % of iron will interfere in the determination. The principle bases on fusion of a test portion with sodium carbonate and extraction of the molten mass with hydrochloric acid. Formation of a complex by the addition of the disodium salt of ethylenediamintetra-ecetic acid (EDTA). Decomposition of the complex by sodium fluoride followed by titration of the liberated EDTA with a standard volumetric solution of zinc chloride in the presence of xylenol orange as indicator.