Isolation and Drying
1. Collect the crystals on a Büchner or Hirsch funnel by vacuum filtration and wash the filter cake with two small portions of cold water. Press the crystals as dry as possible on the funnel with a clean cork or spatula.
2. Spread the benzoic acid on a watch-glass, protecting it from airborne contaminants with a piece of filter paper, and air-dry it at room temperature or in an oven.
Caution: Be certain that the temperature of the oven is below the melting point of the product!
Analysis: Determine the melting points of the recrystallized benzoic acid, the weight of the latter material, and calculate your percent recovery using the following equation.
Percent recovery = Amount recovered (mg)/Amount dissolved (mg) X 100%