Chelatometric Titration of Cobalt and Nickel with Gallein as Indicator

In continuation of a series of chelatometric titration of metal ion with gallein indicator, two procedures for the EDTA titration of cobalt and nickel using gallein as indicator were proposed. In one procedure cobalt ion was titrated with standard 0.05 M EDTA solution in ammonium chloride buffer by stepwise addition of ammonia to keep the p H at the optimum value of 8. A sharp color change from violet to rose red indicating the end point can be observed. In another procedure nickel ion was titrated with standard 0.05 M EDTA solution at p H 8 to 9 in ammonia‐ammonium chloride buffer solution. The end point is indicated by a color change from bluish violet to rose red. The interference caused by the presence of approximately equal molar concentration of various foreign ions was observed.