COMPLEXOMETRIC DETERMINATION OF ZINC USING HYDROXYTRIAZENE AS A METALLOCHROMIC INDICATOR

Abstract

New metallochromic indicators belonging to the class of hydroxytriazenes has been evaluated for the direct complexometric determination of Zinc in the presence of diverse ions. Reagent no (i), (ii) and (iii) has been found to be excellent indicators in the titration with EDTA at pH 6.95-7.50, 6.90-7.60 and 7.00-7.50 respectively. The colour at the end point was from light green to colourless and the titration was carried out between temperature range of 20-600C. Cl- , Br- ,CH3COO- , CO3 2- , SO4 2- , NO2 - , SO3 2- , F- , NO3 - , I- , S 2- , WO4 2- , MO7O24 6- , NH4 + , Na+ , K+ , U(VI), Mn(II), Ba(II), Hg(II), Sn(II), Cd(II), Mg(II), Ca (II), Zr(IV) can be tolerated in the titration of zinc (II) when they are present in equivalent amount with that of zinc (II). However, PO4 3- , Co (II), Cu (II) and Ni (II) interferes and when present in the environmental samples, separation techniques such as masking and demasking agents must be employed. The utility of the technique was checked by using 3-Hydroxy-3-m-toly-1-0-Carboxyphenyltriazene for estimation of zinc in zinc-copper alloy and the results had a maximum relative error of +1.53 and standard deviation of ±0.0378 using Sodium thiosulphate to mask copper ions, hence the study clearly indicated that reagent no (i) and (ii) which have high sensitivity, high selectivity and fairly a wide pH range can be used as metallochromic indicators for estimation of zinc in environmental sample where zinc is the major element.