Estimation of sodium chloride

• In pharmaceutical analysis, the estimation of sodium chloride (NaCl) can be done through precipitation titrations.
• Precipitation titrations are a type of volumetric analysis where a precipitating agent is added to the sample to cause the formation of a solid precipitate.
• The endpoint of the titration is reached when all of the analyte has reacted to form the precipitate, and this can be detected using an appropriate indicator or by observing a change in some physical property.

Here are the steps involved in estimating sodium chloride using a precipitation titration:

Reagents and Equipment:

1. Sample: Pharmaceutical sample containing sodium chloride.
2. Standard Solution: Standardized silver nitrate (AgNO₃) solution.
3. Indicator: Potassium chromate (K₂CrO₄), which forms a reddish-brown precipitate (Ag₂CrO₄) at the endpoint.
4. Glassware: Burettes, pipettes, beakers, and Erlenmeyer flasks for accurate measurements.
5. Stirring rod: For mixing the solution during titration.

Procedure of Estimation of sodium chloride:

1. Preparation of the Sample:

   • Weigh a known amount of the pharmaceutical sample containing sodium chloride.
   • Dissolve it in distilled water in a beaker.

2. Add Indicator:

   • Add a few drops of potassium chromate (K₂CrO₄) indicator to the solution.
   • The solution will turn yellow due to the presence of chromate ions.

3. Titration:

   • Titrate the sample solution with standardized AgNO₃ solution using a burette.
   • Silver ions (Ag⁺) react with chloride ions (Cl⁻) to form a white precipitate of silver chloride (AgCl).
   • Reaction:
     AgNO₃ + NaCl → AgCl + NaNO₃
   • Continue adding AgNO₃ until the endpoint is reached, which is indicated by a color change from yellow to reddish-brown due to the formation of silver chromate (Ag₂CrO₄).

4. Note the Volume:

   • Record the volume of AgNO₃ solution used to reach the endpoint.

5. Calculations:

   • Use the following formula to calculate the amount of NaCl in the sample:
     

     Amount of NaCl (g) = (Volume of AgNO₃ (mL) × Normality of AgNO₃ × Molecular weight of NaCl) / 1

   • Molecular weight of NaCl = 58.44 g/mol.

6. Express Results:

   • Report the result as the percentage of sodium chloride in the pharmaceutical sample.

Thank you for reading from Firsthope's notes, don't forget to check YouTube videos!