Chrominfo: Assay of sodium bicarbonate

Learn about the assay of sodium bicarbonate through a laboratory experiment or practical.

Aim:

To determine the percentage purity (assay) of sodium bicarbonate in a given sample using standard 1 N HCl.

Reference: USP Pharmacopoeia, USP31–NF26 Page 3240

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

Chemicals: Sodium bicarbonate (NaHCO3), methyl red TS, and hydrochloric acid (HCL), etc.

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 03.00 gm of sodium bicarbonate and pour it into a conical flask, and mix with 100 ml of water.
Then, as an indicator, add 2-3 drops of methyl red TS and properly mix it.
Titrate the sample solution with standardized 1 N hydrochloric acid until the endpoint is reached.
Add the HCl slowly, with constant stirring, until the solution becomes faintly pink.
Bring the solution to a boil, then cool and repeat the titration until the faint pink color no longer fades after boiling.
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 sodium bicarbonate.
Each mL of 1 N hydrochloric acid is equivalent to 84.01 mg of NaHCO3.