Note-book of materia medica, pharmacology and therapeutics / by R.E. Scoresby-Jackson.

  • Robert Scoresby Jackson
Date:
1895
Catalogue details

Licence: Public Domain Mark

Credit: Note-book of materia medica, pharmacology and therapeutics / by R.E. Scoresby-Jackson. Source: Wellcome Collection.

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    Volatile or Essential Oils.—These oils are largely used in medicine for a variety of purposes, besides that of imparting an agreeable taste and odour to offensive drugs. They are found most abundantly in the leaves and flowers of plants, from which they are obtained by distillation with water, or, in some instances, by expression from the cellular structure. The delicate and fugitive character of some of these oils demands most careful attention to the process of distilla- tion. Volatile oils, when quite pure, are believed to be invariably colourless, though some have never yet been obtained in that state ; and all, when exposed to air and light, readily assume a certain colour. Their odour is similar to that of the plants yielding them, but they are seldom agreeable in the concentrated form. The readiest way to ascertain the true odour is to rub a drop on the hand, and then breathe upon it, or allow a little to be diffused through the air of an apartment. The essential oils, owing to their value, are greatly subjected to adulteration. By careful fractional distillation they may be separated into two parts, called Eloeoptene and Stearop- tene {i’hotiov, oil, fat, and vrovig, volatile), wdiich have different specific gravities. The former of these is frequently a hydrocarbon, and the latter an oxyhydrocarbon, which in some instances is concrete, and frequently has the composition of ordinary camphor. The volatile oils may be chemically defined as :—1. Hydrocarbons or Camplienes, constituted of C and H. Of this group oil of turpentine may be regarded as the type, with which, although their sensible properties vary considerably, the oils of lemon, bergamot, orange, juniper, and others, are isomeric. 2. Oxyhydrocarbons, containing, in addition to C and H, oxygen, which may exist either in both the Eloeoptene and Stearoptene, or in the latter only. These oxygen- ated essential oils are the most soluble of the volatile oils in alcohol and water, and are extensively used in the form of medicated waters. This class includes also camphor and its modifications. 3. Sul- phuretted and Nitrogenated Oils.—Many of the plants containing these oils are used for culinary purposes, as horse-radish and garlic. Except assafcetida, sagapenum, and garlic, all the oils of this class are derived from the Oruciferce. There are a few volatile oils which contain nitrogen in the form of prussic acid ; they are chiefly derived from the sub-order Amygdalce of the Rosacece. Resins are widely diffused through the vegetable kingdom, and are obtained either by spontaneous exudation, or by iifcisions made into the bark or wood of trees and shrubs. On exposure to the atmosphere the essential oil with which they are united either evaporates or solidifies by oxidation, and the resin resumes its
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