Complexometric Titration of Nickel

Since a suitable indicator is not always available for the direct titration against EDTA, a back titration is recommended (Sec.2.2.4) where a known excess of standard EDTA solution is added to an aliquot of the nickel solution, back titrating the excess against standard ZnS04 solution. To 25.00 cm of 0.1 M Ni(ll) solution, add a known excess (50.00 cm ) of the standardised O.l.M. EDTA solution in a 400 cm conical flask. Dilute the solution to about 200 cm and add 4 cm of the buffer solution (pH = 10) and 1-2 drops of Eriochrome Black T indicator. Titrate the excess of EDTA with standard 0.1 M zinc sulphate solution until the colour changes sharply from blue to greenish red. Repeat to obtain concordant results. Calculate, from the average titre, the concentration of nickel(II) in g dm  

2 Gravimetric determination of nickel A solution of dimethylglyoxime in ethanol precipitat3es ions from hot fliintly acidic solution. If the disodium salt of the reagent is available, a 2% solution is used to precipitate the red square planar diamaquatic complex (Fig. 15.1). 

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