Separation and gravimetric determination of iron using oximidobenzotetronic acid

Using oximidobenzotetronic acid (OBTA) as a reagent, iron (II) has been separated and accurately determined gravimetrically in presence of 10-fold or more of Mn(II), Al(III), Cr(III), Ti(IV), Zr(IV), Th(IV), Ni(II), Zn (II), Mo (VI), Ca (II) Mg(II), tartrate, citrate, acetate, phosphate, sulphocyanide, fluoride W (VI), Cu (II), Bi (III) and Sn (II). Ce (IV), Ce (III), Co (II), V (V) and EDTA, however, interfere in the determination.