This document provides instructions for estimating the amount of nickel (Ni) in a sample using complexometric titration with EDTA. The procedure involves: 1) Standardizing a solution of EDTA against zinc sulfate to determine its concentration. 2) Dissolving a nickel sample and filtering the solution. 3) Titrating an aliquot of the nickel solution against EDTA using murexide indicator, which changes color from yellow to red at the endpoint. 4) Calculating the concentration of nickel in the original sample and percentage of nickel in the complex from titration results.

1. SHREE MALLIKARJUN COLLEGE CLASS:TYBSC
SAFETY: Refer to MSDSof Ethylenediaminetetraacetic acid disodium salt, ammonium hydroxide, ammonium chloride,
murexide, Eriochrome Black-T (EBT), zinc sulphate. -Dr. Mithil S. Fal Desai
Aim: Estimate the amount of Ni by EDTA.
Chemicals: Ethylenediaminetetraacetic acid disodium salt (EDTA), nickel complex, ammonium
hydroxide, ammonium chloride, murexide, Eriochrome Black-T (EBT), zinc sulphate.
Apparatus: Standard volumetric flask, pipette, burette, conical flask, beakers, funnel and glass
rod.
Theory: In the complexometric titration of Ni2+ and EDTA, murexide is used as an indicator. The
titration is carried out in the presence of ammonia buffer at pH 10. The metal-indicator complex
is yellow, while the color of the indicator in the buffer solution is red.
Ni2+ + Na2C10H14N2O8  [NiC10H12N2O8]2- + 2Na+ + 2H+
Zn2+ + Na2C10H14N2O8  [ZnC10H12N2O8]2- + 2Na+ + 2H+
Procedure:
A) Preparation of 0.01M EDTA (100 mL) calculate
B) Preparation of 0.01M ZnSO4.H2O (100 mL) calculate
C) Preparation of buffer of pH 10
Dissolve 32 g of NH4Cl in 300 mL of 28-30% ammonia solution. Slowly and carefully add 200
mL distilled water.
D) Standardization of EDTA salt solution (~0.01M)
Rinse and fill the burette with EDTA salt solution. Pipette out 10 mL of 0.01M of ZnSO4 solution
and add 10 mL of a buffer of pH 10. Add 2-3 drops of EBT indicator solution to the flask. Titrate
the solution from the flask against EDTA until the wine red color of the solution changes to blue.
Repeat the titration to get constant readings.
E) Estimation of Ni2+ ions.
Weigh the exact amount (~0.2 g) of the nickel complex and transfer it quantitatively in 250 mL
beaker. Add 1.0 mL of concentrated HCl and heat to evaporate the content from the beaker. Repeat
the above decomposition procedure three times. Finally, boil the content of the beaker with 0.5
mL concentrated HCl and 50 mL of water. Filter this solution through Whatman No. 1. Collect the
filtrate quantitatively in a clean 100 mL standard volumetric flask. Pipette out 10 mL of this nickel
solution in a clean conical flask. Add 10 mL of buffer solution and a pinch of murexide ground
with sodium chloride (0.1 g of indicator in 20.0 g of NaCl). Titrate slowly with EDTA solution.
Continue titration until the solution color changes from yellow to red. Repeat the titration to get
constant readings.
Results: i) Strength of EDTA solution =____M
ii) Strength of given Ni2+ ion solution =____M
iii) Amount of Ni2+ in given complex = ____g/100 mL
iv) Theoretical percentage of Ni in complex = ____%
v) Experimental percentage of Ni in complex = ____%
Further reading: Vogel’s textbook of quantitative chemical analysis, J. Mendham, R. C. Denney,
J. D. Barns, M. Thomas, B. Sivasankar, Pearson India Education, 6th Edition.