1. Title; To determine the purity of benzoic acid crystals by melting point determination.

2. ThermometerCapillary tube Benzoic acid crystals Aluminium block Bunsen burner 122

3. Procedure Seal one end of a capillary tube. Dip the open end in the benzoic acid and catch a small quantity of the crystals. Tap the closed end off the desk top until the crystals have lodged there. Place the capillary tube in the melting point apparatus as shown above. Heat the aluminium block until the crystals melt. Note the temperature (123 degrees for benzoic acid).

4. Discussion If the crystals melt exactly at their correct melting point they are very pure. If they melt at a lower or higher temperature and take 4 or 5 degrees to melt, they are impure.