Friday, December 31, 2021

Assay of magnesium sulphate

Learn about the assay of magnesium sulphate through a laboratory experiment or practical.

Aim:

To determine the percentage purity of magnesium sulphate using standard 0.1 N EDTA (Direct titration).

Requirements:

Glasswares: Burette, burette stand, conical flask, volumetric pipette, beaker, volumetric flask, funnel, glass rod, and wash bottle, etc.

Chemicals: Magnesium sulphate heptahydrate (MgSO4), disodium edetate (EDTA), ammonia (NH3), calcium chloride (CaCl2), ammonium chloride (NH4Cl), and solochrome black-T indicator or mordant black II, etc.

Reaction Involved:

The assay of MgSO4.7H2O is based upon the reactions designated by the following equations:
Mg2+ + [H2X]2‑→ [MgX]‑ + 2H+

Preparation and standardization of 0.05 M EDTA solution:
Click here to get the procedure.

Preparation of strong ammonia-ammonium chloride solution:
Click here to get the procedure.

Titration procedure:

  • All glassware should be cleaned and dried according to standard laboratory procedures.
  • Before filling the burette for the titration, rinse it with distilled water and then pre-rinse it with a portion of the titrant solution. Pre-rinsing is required to make sure that all solution in the burette is the desired solution, not a contaminated or diluted solution.
  • Take the unknown stock solution of titrant in a clean and dry beaker then fill the burette using the funnel.
  • Remove air bubbles from the burette and adjust the reading to zero.
  • Take 0.3 gm of magnesium sulphate and pour it into a conical flask, and dissolve in 50 ml of warm water.
  • Using a pipette, add 10.00 ml of strong ammonia-ammonium chloride solution.
  • Then, as an indicator, add 2-3 drops of mordant black II mixture and properly mix it.
  • Titrate the sample solution with standardized 0.05 disodium edetate until the endpoint is reached.
  • The actual endpoint is indicates by the pink color is discharged from the blue.
  • Properly record the readings of the burette.
  • To get accurate results, repeat the titration three times.
  • Take their mean and calculate the percentage purity of magnesium sulphate.
  • Each ml of 0.05 M disodium ethylene diamine tetracetate is equivalent to 0.00602 g of MgSO4.

Observation table:

Sr. No.

Content in conical flask

Burette reading

Volume of titrant used (ml)

Initial

Final

1

 

 

 

 

2

 

 

 

3

 

 

 

 

Mean:


Result:

The percentage purity of the magnesium sulphate (MgSO4) sample was found to be_____.


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