Determination of nickel in a nickel(II) salt using EDTA

Essay by jamesfstanleyHigh School, 12th gradeB, September 2014

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EDTA (H₄Y) is widely used to determine metals in complexometric (a volumetric analysis where the formation of a coloured complex is used to indicate the end point of a titration) titrations as it forms stable complexes with most metal ions. EDTA is a tetracorboxylic acid and in alkaline conditions, it exists as Y⁴⁻ ions, which form 1:1 complexes with metal ions like nickel(II) ions:

Y⁴⁻ + Ni²⁺ NiY²⁻

A metal ion indicator (an organic dye which changes colour when it binds with metal ions) shows the end of an EDTA complexometric titration. However, for a metal ion indicator to be suitable in n EDTA titration, it must not bind as strongly with metal ions as EDTA does. Murexide is therefore suitable.


The aim of this experiment is to determine the percentage of nickel in a nickel(II) salt using EDTA.


The following apparatus was collected:

50cmᶟ burette ●Glass stirring rod

20cmᶟ pipette ●Hydrated nickel(II) sulphate (NiSO₄.6H₂O)

100cmᶟ standard flask ●Standardised 0.10moll⁻¹ EDTA solution

250cmᶟ conical flask ●1 moll⁻¹ ammonium chloride

Weighing bottle ●Murexide indicator

Balance (accurate to 0.01g) ●0.88 aqueous ammonia

100cmᶟ beakers ●Deionised water

25cmᶟ measuring cylinder

Wash bottle

Pipette filler

White tile

Filter funnel

Approximately 2.6g of hydrated nickel(II) sulphate was transferred to a weighing bottle and the contents weighed and about 25cmᶟ of deionised water was added to a 100cmᶟ beaker and the nickel transferred to the water. The bottle was weighed without any remaining salt and then the mixture was stirred until the solid was dissolved before the resulting solution was transferred to a 100cmᶟ standard flask.

The beaker was then rinsed several times with deionised water and the rinsings were added to the standard flask. The solution was filled up to the graduation mark with deionised water and the flask was stoppered and...