Study of Complexing Equilibria of Hafnium with Chrome Azurol S in Aqueous Solution

Department of Chemistry, Nagpur University Campus, Nagpur, Manuscript received 28 July 1973 ; accepted 7 January 1974 Chrome Azurol S is proposed as a sensitive and selective chelating reagent for the spectrophotome­tric determination of hafnium. Chelate formation is a function of acid concentration of the solution. The chelates 1:1 and 1:2 (metal : ligand) exist simultaneously from pH 1. 0 to 1. 3. At pH 1. 5 only 1:1 chelate is found to exist while at pH 2. 0 and above, 2:1 (metal : ligand) chelate exists. At higher pH the chelate precipitates out due to the hydrolysis of hafnium. The stability of chelate, its composition and analytical applications are investigated. Certain masking reagents are also suggested for eliminating the effects of interfering metal ions, in the determination of hafnium with chrome Azurol S