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Complexometric determination of zinc



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Fundamentals of Analytical Chemistry Amazon

Fundamentals of Analytical Chemistry

by Douglas A. Skoog and others

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Complexometric titration » EDTA - titration of zinc

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general remarks

Zinc is determined by EDTA titration in almost the same way magnesium is - in the pH 10 against Eriochrome Black T. If the solution initially contains also different metal ions, they should be removed or masked, as EDTA react easily with most cations (with the exception of alkali metals).


Reaction taking place during titration is

Zn2+ + EDTA4- → ZnEDTA2-

sample size

For 0.01 M titrant and assuming 50 mL burette, aliquot taken for titration should contain about 0.35-0.45 millimoles of zinc (23-29 mg). If preparation of such sample is difficult, we can use different EDTA concentration.

end point detection

End point of zinc titration is easily detected with Eriochrome Black T.

solutions used

To perform titration we will need titrant - 0.01 M EDTA solution and ammonia pH 10.0 buffer. We will also need indicator - either in the form of solution, or ground with NaCl - 100 mg of indicator plus 20 g of analytical grade NaCl.


Procedure to follow doesn't differ from the one used for the magnesium titration.

result calculation

Calculation of EDTA titration results is always easy, as EDTA reacts with all metal ions in 1:1 ratio:

Zn2+ + EDTA4- → ZnEDTA2-

That means number of moles of zinc is exactly that of number of moles of EDTA used.

To calculate zinc solution concentration use EBAS - stoichiometry calculator. Download determination of zinc reaction file, open it with the free trial version of the stoichiometry calculator.

Click n=CV button above EDTA4+ in the input frame, enter volume and concentration of the titrant used. Click Use button. Read mass of zinc in the titrated sample in the output frame.

sources of errors

In general this is a simple titration, with no other problems then those listed as general sources of titration errors.

Page was last modified on September 06 2009, 00:14:20.

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