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