Essential Oils


The Fact About Essential Oils

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The Fact About Essential Oils

Aromatic Essences are volatile, oily, fragrant substances, which can be obtained from plants in a variety of ways: sometimes by pressing (e.g. cloves, sometimes by tapping (laurel, liquid Borneo camphor), sometimes by separation using heat (turpentine), in some cases by solvents, or by enfleurage (i.e. absorption of the perfume by a greasy substance from which it is afterwards separated).

Very often the essential oils are present-in such small quantities in comparison with the mass of the plant, and they adhere so strongly to the plants  that contain them, that distillation of the plant is necessary. The normal method of procedure is very similar to that used in the production of distilled water; however, the same water must be distilled with further quantities of substances, since if this is not done a considerable quantity of essence will be lost.

Certain of these essential oils do appear in the pharmacopoeiae of the world. In France, the 1949 edition - Codex V11 - contains about fifteen. Earlier editions contained many more - twenty four in 1937, forty - four in 1837

Certain of these essential oils do appear in the pharmacopoeiae of the world. In France, the 1949 edition - Codex V11 - contains about fifteen. Earlier editions contained many more - twenty four in 1937, forty -four in 1837.

Aromatic essences in general pre-exist in plants, though there are some which form only in the presence of water. Though generally colorless, a few essences are distinctively colored: the essence of cinnamon, for instance is reddish, the essence of chamomile, blue and the essence of wormwood, green. Some (e.g. the essences of bitter almonds, cinnamon and garlic) are heavier than water, but most are lighter. Again although most essences are liquids, some are solids.

Essences are to be distinguished from fatty oils, which are fixed and stain a paper permanently., in that they are colatized by heat and their stain is temporary. They are soluble in alcohol, ether and fixed oils and insoluble in water, to which they nevertheless impart their odor.

The boiling points from 160 to 240C. and their densities from 0.759 to 1.096. They may be dextro-rotatory or laevo-rotatory, rarely inactive, to polarised light.

The Requirements Of Codex

The requirements of the codex  demand a minimum standard of analysis of physical properties (density, solubility in alcohols of various strengths and in other solvents, boiling point, polarimetric deviation, refractive index, melting point, etc) and chemical properties (research and dosages of one of the constituents or of a combination which forms a chemical function - for example, phenols, aldehydes, alcohols, etc) To avoid overloading the present work I have mentioned only a few of the details which are generally without use to the practitioner.

They dissolve grease, iodine, Sulphur and phosphorous. They reduce certain salts.

They are stimulants which can be used both internally and externally, usually in a solution of alcohol or another suitable solvent, although they can be used neat. They are also perfumes.

There was a time when essences were considered to be definite substances, but with the birth of the science of organic chemistry at the end of the nineteenth century, they gradually began to yield up their secrets - though even today all has not yet been revealed. Dr Taylor of the University of Austin. Texas has observed that essences present  more new compounds than the chemists of the whole world could analyse in a thousand years. At least we now know that they are mixtures of many constituents: terpenes, alcohols, esters, aldehydes, ketones and phenols, etc. Without going into unnecessary detail here, I should add that they have been divided into three groups according to their elementary composition:

  • Hydrocarbon essences, 1.e. those rich in terpenes (e.g. the essences of turpentine and lemon): these are the most numerous.
  • Oxygenised essences (e.g. the essences of rose and mint) these are generally solid essences.
  • Sulphuretted essences (the Cruciferae and liliaceae)

Many essences are a mixture of carbides and oxygenised substances in which one finds most of the chemical functions of organic matter: hydrocarbons or terpenes such as thymen, alcohols such as geraniol and linalol, aldehydes like the essences of bitter almonds and citral, esters like the acetates of bornyl and linalyl, ketones like carvone and thujone, and phenols like eugenol, thymol and carvacrol.

Some essences whose composition have been clearly defined , or at least appears to have been, are reproduced synthetically: but there are good grounds for believing that the results obtained with synthetic essences cannot be compared with the effects of natural essential oils, and practice bears this out.

The whole natural essence is found to be more active that its principal constituent. Moreover, those constituents which form a smaller percentage of the whole are found to be more active than the principle constituent (this is an example of synergy). As early as 1904 Cuhbert Hall demonstrated that the anti-septic properties of the essence of eucalyptus were much mor powerful than those of its principal constituent, eucalyptol.

"It is not enough," wrote M.Huerre in 1919, "to place side by side the principal chemical elements which analysis shows to be present in a particular vegetable essence, in order to obtain a product which, therapeutically speaking, is as active as that of the natural essence."

Dextrorotatory: rotating to the right, especially rotating thus the plan of polarization of light: laevorotatory: rotating the plane of polarization of light to the left (these characteristics are used to differentiate various bodies).

Reference: The Practice Of Aromatherapy Dr Jean Valnet


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