Essential oils must be removed from the basil. For these purposes, solvent extraction is used in which oil is better dissolved. Then the oil and solvent are separated by distillation. If the solvent is added to the basil, and then distilled, the solvent will evaporate and the oil will remain in the basil. The plant will absorb oil again.

Dear Ying,

Essential oils have high boiling point, and well may decompose at that temperatures. Steam distillation opens the way to separate essential oils from plant parts without organic solvents. When steam goes through the plant parts, it blows away organic vapors (most essential oils have small, but not negligible vapor pressure at 100 ° C). After the condenser (in the receiver flask), mixture of water and oil separates spontaneously. You can read more in wiki (https://en.wikipedia.org/wiki/Steam_distillation) or in some chemical engineering textbook. However, organic solvents must be used if compound of interest decomposes already at 100 ° C.

Hi, yes you may use solvent distillation technique for some smaller molecule essential oil. However, it might not suitable for higher molecular weight essential oil and those are heat sensitive.

Actually you can buy some homemade fragrance oil (lavender etc) from market that are obtained using water distillation technique, due to the simplicity of setup.

If you are in research basis, it is more recommended that using other techniques to obtain essential oil, in order to prevent any degradation of your product. Example :

Solvent extraction, supercritical fluid extraction, microwave assisted extraction (depend on component), sonication (depend on component) etc.

Hereby I attach a document for your reference, hope it helps.

The reason why water iis used as the choicest solvent for etraction of essential oils from plant parts is as explained by Novikov iis 1. Essential oils have a higher boiling point and the vapour pressure of the oil at 100 degree Celsius is much less and hence it forms an azeotrope with water and distill over at a lower temperature.2. Most of the essential oils are immissible with water and they form a separate layer which allows its easy separation. 3. Majority of the essential oils are lighter than water and hence on condensation they float on top. Finally water to the cheapest extraction medium available.

I agree Varughese above. But would point out that the problem qith solvent extraction and even supercritical fluid extraction is that other plant components are extracted as well as the essential oil. some of these have unpleasant odours and are dften difficult to separate from the essential oil itself

Thank you John, I agree with you.

Thank you Varughese. You explained it all; and the main problem is the separation of solvent and essential oil, as explained by John.

For the extraction essential oil, the method that recommended in the pharmacopeia is hydrodistillation. Otherwise, you have other methods not inscrived in pharmacopeia, such as method with solvent that have minimum of toxicity and higher selectivity but in this case the final product is called essence. So you must separate volatile fraction from solvent.

If you use organic solvent you will lose your oil because it will dissolved and mixed with solvent. How to separate them?

Using water is more suitable to separate oil and water which are immiscible.

hydrodestillation is the recomended method

It is possible to force the separation of essential oils (from water) that are not very hydrophobic, with salt addition, for example?