“…The following diverse ions do not interfere in the determination of 15 pg Th(IV) 10 ml -': Fluoride, Zr4+ U4 + , F.e 3+ , Pb2+ , Cu 2+ , V s+ , Ni 2+ , Cd2+ , Zn 2+ , Sn 2+ in the range (0.02-1.2).mg; Nb5+ Mo5+ W6, Re7+ Pd 2 + , Ga 2+ , A1 3+ , Sb 3+ , Co 2+ , Cr3+ Hg2+, Mn z+ , Mgz + in the range (3.5-8.0) mg; acetate, tartrate, oxalate, thiourea, ascorbic acid in the range (15.0-20.0) mg. Fe(III) interferes when present in a 30-fold excess. However, its reduction-to Fe(II) by ascorbic acid (1 ml, 2%) increases the tolerable amount up to 0.8 mg. Interferences due to U(IV) and Zr(IV) were avoided by oxidation of U(IV) to U(VI) with perchloric acid [10] and masking with tartaric acid (0.2 ml, 10%), respectively.…”