SPECTROPHOTOMETRIC DETERMINATION OF INDIUM IN ZINC EFFLUENT

A new extraction-spectrophotometric method for the determination of in dium at ppb level in zinc effluent is described. It is based on quanti tative extraction (51.2-99.2%) of the tetrabromoindate complex with to luene solution of N,N'-diphenylbenzamidine and its nine analogous from sulphuric acid solutions, which allowed the extract to react with bas ic dye (i.e. brilliant green, malachite green, crystal violet) solutio n in sequence. Among the basic dyes tested, brilliant green gave the m ost sensitive colour reaction. The value of molar absorptivity of the amidine bromoindate extracts with brilliant green lie in the range of( 0.53-1.03) x 10(5) 1 mole(-1) cm(-1) at absorption maximum, 630-640. W ith the most sensitive compound, N-(2-methyl-phenyl)-N-phenylbenzamidi ne the detection limit of the method is 13 ppb. The method is free fro m interferences of almost all ions associated with indium. The method has been applied for the determination of indium to zinc-effluent.