Oils

Oils are classified under five important heads.

1. Volatile oils,
2. Drying oils,
3. Semi-drying oils,
4. Non-drying oils and
5. Vegetable fats.

Volatile oils will evaporate on exposure to air. Lemon grass oil is an example for this. They are usually prepared by the process of distillation in steam. They are used in perfumery and as flavouring agents. The other four types of oils are obtained by

1. Expression when the material is crushed in a press and the oil is squeezed out.
2. By extraction when the oil is dissolved by suitable solvent. Oils are used in cooking, medicine, manufacture of soaps, paints etc.