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Estimation of Sodium Benzoate

  • Sodium benzoate is a common preservative used in food, medications, and cosmetics.

  • Its estimation is important to ensure product safety and compliance with regulations.

  • The quantitative determination of sodium benzoate can be conducted using various methods, including UV spectroscopy, high-performance liquid chromatography (HPLC), and titration.

 illustrating the use of Sodium Benzoate as a preservative across food, cosmetic, and medication products
illustrating the use of Sodium Benzoate as a preservative across food, cosmetic, and medication products

Here's an overview of a typical titration method for estimating sodium benzoate in a sample:

Materials:

  • Sodium benzoate sample

  • Distilled water

  • 0.1M Hydrochloric acid (HCl)

  • 0.1M Sodium hydroxide (NaOH)

  • Phenolphthalein indicator

Procedure:

1. Preparation of Sample:

  • Dissolve a known weight of the sample containing sodium benzoate in distilled water.

  • Make sure the solution volume is known for concentration calculations.

2. Acidification:

  • Add a few drops of phenolphthalein indicator to the sodium benzoate solution.

  • Titrate with 0.1M HCl until the pink color disappears.

  • This step ensures that all the benzoate is converted to its acidic form (benzoic acid).

3. Back Titration:

  • After acidification, add a known excess amount of 0.1M NaOH to the mixture.

  • The solution will turn pink again.

  • Now, titrate this solution with 0.1M HCl until the pink color just disappears. Record the volume of HCl used.

4. Calculation:

  • The amount of NaOH that reacted with the sodium benzoate can be calculated by the total amount of NaOH added minus the amount of HCl used in the back titration.

  • From the moles of NaOH reacted, determine the moles of sodium benzoate (since they react in a 1:1 ratio).

  • Finally, calculate the concentration of sodium benzoate in the sample based on the initial volume of the sample solution.


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