Getting the oil out

Three of the techniques from section 3.3 are used to extract essential oils, and which one is chosen depends on the plant material.

Steam distillation

Separation techniques such as steam distillation and solvent extraction are used for the extraction of essential oils. Oil is obtained from cinnamon leaves by passing steam through those leaves.

Figure to be added

An industrial steam distillation plant in section: a steam generator over a fire on the left, its steam piped into a tall vessel packed with cinnamon leaves, and a coiled condenser on the right delivering into a collecting bottle.

Here the steam leaving the steam generator travels over the heated plant parts. The essential oil vaporises mixed with water vapour at a temperature below 100 °C. By condensing that vapour mixture the essential oil and water are obtained. Because they do not mix, they can be obtained separately.

Solvent extraction

Extraction by means of a solvent is another method of extracting essential oils. In this method organic solvents such as ether, chloroform and toluene are used. When the plant parts are mixed with the solvent and shaken, the essential oil dissolves in the solvent. By evaporating off the solution, the essential oil is separated out.

Pressing

The volatile oils contained in some plant parts can also be obtained by pressing them under a suitable pressure.

Steam distillation, solvent extraction and pressing all recover the same kind of compound. The method is chosen by asking what the plant material will survive, and how much oil there is to be had.