Learn about the assay of calcium gluconate through a laboratory experiment or practical.
This experiment is performed in two parts i.e.
A: Preparation and standardization of 0.05 M EDTA solution.
B: Assay of calcium gluconate
Aim:
To perform the assay of calcium gluconate using standard 0.1 N EDTA (Replacement titration).
Requirements:
Glasswares: Burette, burette stand, conical flask, volumetric pipette, beaker, volumetric flask, funnel, glass rod, and wash bottle, etc.
Chemicals: LR grade calcium gluconate (C12H22CaO14), disodium edetate (EDTA), ammonia (NH3), calcium chloride (CaCl2), ammonium chloride (NH4Cl), magnesium sulphate ( MgSO4), hydrochloric acid (HCL), and solochrome black-T indicator or mordant black II, etc.
Apparatus: Digital/analytical balance, and Ultrasonicator.
Principle of assay of calcium gluconate:
The assay of calcium gluconate is based upon a replacement complexometric titration. Magnesium forms a complex with the mixture of indicator mordant black II which indicates the first color.
The magnesium-indicator complex is more stable compared to the calcium-indicator complex; hence calcium does not affect the magnesium-indicator complex. When titrated against disodium edetate, calcium and EDTA formed.
When all of the calcium has been consumed, the drop of EDTA breaks the magnesium-indicator complex, allowing the free indicator to form a complex with the magnesium. The endpoint is determined by detecting the second color at that time.
The following is the reaction that is involved in this titration.
Preparation of 0.05 M magnesium sulphate:
Take 600 mg of anhydrous MgSO4 and dissolve in 50 ml of distilled water in a volumetric flask, and properly mixing it. Once it has completely dissolved, make up the volume to 100 ml.
Preparation of strong ammonia-ammonium chloride solution:
Take 10 ml of water and 20 ml of strong ammonia solution in a beaker and saturate it with ammonium chloride.
Click here to get the procedure of preparation and standardization of 0.05 M EDTA solution.
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 0.5 gm of calcium gluconate and pour it into a conical flask, and dissolve in 50 ml of warm water.
- Allow the solution to cool to ambient temperature, add 05 ml of 0.05 M magnesium sulphate solution
- Using a pipette, add 10.00 ml of strong ammonia-ammonium chloride solution.
- Then, as an indicator, add 2 drops of mordant black II mixture and properly mix it.
- Titrate the sample solution with standardized disodium edetate until the endpoint is reached. The actual endpoint is indicated by a change in the color of the solution.
- 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 calcium gluconate.
- For a blank reading (B), repeat the titration using the same procedure but without the calcium gluconate.
Observation table:
|
Sr. No. |
Content
in conical flask |
Burette
reading |
Volume
of titrant used (ml) |
|
|
Initial |
Final |
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|
1 |
|
|
|
|
|
2 |
|
|
|
|
|
3 |
|
|
|
|
|
Mean: |
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Calculations:
Percentage Purity = V x E x AM x 100/ W x RM
Where,
V is a volume of EDTA used
V = A – B
A is the volume of EDTA used in the titration with calcium gluconate
B is the volume of EDTA used in the titration without calcium gluconate
E is an equivalent factor
AM is an actual molarity
RM is a required molarity
W is the weight of the sample
For 01 ml of calcium gluconate, the equivalent factor of 0.05 M disodium edetate is 0.02242
Result:
The percentage purity of calcium gluconate was found to be_____.
Commonly asked question on titration of calcium gluconate are as follows.
Assay of calcium gluconate is based on which titration?
Assay of calcium gluconate is based on complexometric titration.
Which reagent is used in the assay of calcium gluconate?
0.05 M magnesium sulphate solution, 0.05 M EDTA solution, and strong ammonia-ammonium chloride solution are used in the assay of calcium gluconate.
Which indicator is used in the assay of calcium gluconate?
Mordant black II indicator is used in the assay of calcium gluconate.
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