Estimation of Sodium Benzoate

• Estimation of Sodium Benzoate is important to ensure product safety and compliance with regulations.
• Sodium benzoate is a common preservative used in food, medications, and cosmetics.
• The quantitative determination of sodium benzoate can be conducted using various methods, including UV spectroscopy, high-performance liquid chromatography (HPLC), and titration.

Typical titration method for estimation of 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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