1. Dissolve the impure calcium hydroxide in a minimum amount of hot water or ethanol. The solvent should be heated to a temperature just below the boiling point to dissolve the maximum amount of calcium hydroxide.
2. Filter the hot solution to remove any insoluble impurities. The solution can be filtered through filter paper or a Büchner funnel.
3. Cool the filtrate slowly. As the solution cools, the calcium hydroxide will start to recrystallize. The solution should be cooled slowly to allow for the formation of large, well-formed crystals.
4. Collect the crystals by filtration. The crystals can be collected using filter paper or a Büchner funnel.
5. Wash the crystals with a small amount of cold solvent. The crystals should be washed with a small amount of cold solvent to remove any remaining impurities.
6. Dry the crystals in a desiccator. The crystals can be dried in a desiccator over a desiccant such as calcium chloride or silica gel.
Once the crystals are dry, they can be used for various applications. Recrystallization is a common technique used to purify a wide variety of compounds.
