Estimation of Magnesium ions in water using EDTA
The principle on which the titration lab is based:
The reaction between Mg2+ ions and EDTA can be represented like this.
Mg2+ + H2Y2- → MgY2- + 2H+
Prepare a standard solution of magnesium sulfate and titrate it against the given EDTA solution using Eriochrome Black T as the indicator. A buffer solution is prepared for maintaining the pH of about 10. When the reaction is complete all the magnesium ions would have been complexed with EDTA and the free indicator would impart a blue color to the solution. Estimation of magnesium ions using edta.
Procedure:
Preparation of 0.025M MgSO4.7H2O: Dissolve 0.616 grams of analytic grade magnesium sulfate into a 100 mL volumetric flask. Dissolve the salt completely using distilled or de-ionized water.
Standardization of EDTA: 20 mL of the standard magnesium sulfate solution is pipetted out into a 250 mL Erlenmeyer flask and diluted to 100 mL . Add 2 mL of a buffer solution of pH 10. Add 4 drops of Eriochrome Black T to the solution. The solution is warmed to 40 degrees C and titrated against EDTA taken in the burette. At the end point the color changes from wine red to blue. Repeat titrations for concordant values.
Estimation of magnesium ions in the given sample: 20 mL of the given sample of solution containing magnesium ions is pipetted into a 250 Erlenmeyer flask, the solution is diluted to 100 mL, warmed to 40 degrees C, 2 mL of a buffer solution of pH 10 is added followed by 4 drops of Eriochrome black T solution. The solution is titrated against the standardized EDTA solution. Repeat the titrations to obtain concordant values. The end point is the color change from red to blue.
Using the volumes of solutions used, their determined molarity, you will be able to calculate the amount of magnesium in the given sample of water.
This is how you can perform an estimation of magnesium using edta.