The benzoic acid Collect the top layer dry with Na2SO4 and evaporate the solvent.
Benzoic acid is sparingly soluble in water and forms a precipitate. The benzoic acid can then be separated by suction filtration through a Buchner funnel. Washing with sodium bicarbonate converts the benzoic acid to the more water-soluble form of sodium benzoate, which is extracted into the aqueous layer. Additionally, sodium bicarbonate neutralizes the catalytic acid in this reaction.
Benzoic acid containing the naphthalene impurity can be purified by crystallization in water. The reaction between benzoic acid and NaOH is an acid-base neutralization reaction. An acid reacts with a base to form salt and water. In aqueous solutions, NaOH increases the solubility of benzoic acid. Benzoic acid cannot move from one layer to another because ethanol is immiscible with water.
