About us | Feedback

Complexometric determination of magnesium



Need more info?

Analytical Chemistry: Theoretical and Metrological Fundamentals Amazon

Analytical Chemistry: Theoretical and Metrological Fundamentals

by K.Danzer

(commisions earned)

Complexometric titration » EDTA - titration of magnesium

Balancer and stoichiometry calculator

operating systems:
XP, Vista, 7, 8, 10

single user license price:
€24.95 - approximately $33

Buy Now!

By clicking Buy Now! you will continue to the FastSpring checkout page where payment will be taken, and your order fulfilled by FastSpring, our trusted reseller, and Merchant of Record.

download 30-day free trial!
30-day money back guarantee!

general remarks

Magnesium can be easily determined by EDTA titration 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). Calcium can be precipitated as carbonate or oxalate, although presence of oxalates may make end point detection difficult.


Reaction taking place during titration is

Mg2+ + EDTA4- → MgEDTA2-

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 magnesium (8.5-11 mg). If preparation of such sample is difficult, we can use different EDTA concentration.

end point detection

End point of magnesium 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 much from the one used for the EDTA standardization.

result calculation

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

Mg2+ + EDTA4- → MgEDTA2-

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

To calculate magnesium solution concentration use EBAS - stoichiometry calculator. Download determination of magnesium 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 magnesium 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. The most likely problem is spotting the end point, which is not always sharp.

Page was last modified on September 06 2009, 00:14:15.

titration at www.titrations.info © 2009 ChemBuddy