NEW METALLOCHROMIC INDICATORS FOR COMPLEXOMETRIC TITRATION OF COPPER (II) IN PRESENCE OF INTERFERING SPECIES

Abstract

Six hydroxytriazenes has been introduced as a metallochromic indicator in the complexometric titration with EDTA and applied successfully to the titration of copper (II). A direct method of titration of Cu (II) with EDTA using these hydroxytriazenes has been proposed. The change of colour of the solution at the end point during titration was from yellow to green at a pH range of 5.5-6.0, 5.05-5.50, 5.0-5.5 for reagent number (i, ii, iii, vi), iv, v respectively. The titration can be performed at the temperature range of 25-60℃. The minimum concentration of copper (II) which can be titrated is as follows: 1.0 x 10−3 M Cu (II), 3.0 x 10−3M Cu (II), 5.0 x 10−3M Cu (II) when using reagent number (i, iii, v, vi), iv, ii respectively as metallochromic indicators. Interference studies of a number of cations and anions have been studied. Cl−, Br−, CH3COO−, PO4 3−, SO4 2−,C2O4 2−, S2O3 2−, NO3 −, SO3 −, S 2−, HPO4 2−, F −, NO3 −, WO4 2−,Mo2O24 6− , I −, NH4 +, Na+, K +, Ba2+, Hg2+, Mg2+, Ca2+ can be tolerated on the titration of Cu (II) up to tenfold excess. However, {U(vi), Sn(II), Zr(iv), Co(II), Zn(II), Ni(II)}, {Pb(II), Th(IV)}, {Mn(II), Cd(II)} interfered at equivalent amounts, fivefold excess, tenfold excess respectively.