THE COMPLEXIMETRIC TITRATION OF ZIRCONIUM BASED ON THE USE OF FERRIC IRON AS THE TITRANT AND D IS ODIUM -1,2 -DIHYDROXYBENZENE -3,5 -DISULFONATE AS THE INDICATOR

摘要

Zirconium is converted to a stable complex by the addition of an excess of disodium dihydrogen ethylene diamine tetra-acetate (EDTA) to a dilute sulfuric acid solution containing zirconium. The excess EDTA is titrated with iron (III) to a disodium-l,2-dihydfoxybenzene-3,5-disulfonate (Tiron) end point at a pH of 4.8. Fluoride ion interferes; by complexing the fluoride with beryllium, however, the titration can be conducted in the presence of as much as 4 g of fluoride. Such anions as sulfate, tartrate and phosphate do not interfere. Cationic interferences are relatively few since most metals form weaker complexes with EDTA than do either zirconium or iron. By slight modifications in the procedure, the method is applicable to the determination of zirconium in the presence of moderate amounts of trivalent iron, divalent nickel and trivalent chromium. The method is rapid and simple. The coefficient of variation is less than one per cent.