Friday, December 31, 2021

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

Requirements:

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.

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 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.

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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