This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol1", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
The aromatics may be given in substance, or in the forms of infusion, tincture, fluid extract, and volatile oil. The form of infusion is much used, and generally very suitable; but it should be remembered that water will dissolve but a small proportion of volatile oil, and, in the case of those particular aromatics which depend for their influence exclusively on the oil. the proportion of the medicine to the menstruum should be small, to avoid waste. Decoction and dry extract are inappropriate forms; as the volatile oil on which their virtues depend is more or less driven off during their preparation. In the fluid extract, if properly made, the oil may be retained; and this is often a very convenient form for use. Tincture is a very appropriate form, whenever the necessary amount of alcohol, used in the preparation, may not be objectionable.
The aromatic oils are frequently preferred, in consequence of their less bulk, their greater power, and their greater convenience of administration. Some of them may be given undiluted, simply dropped on sugar; but most of them are too pungent and powerful to be exhibited in that way. They are, however, often and very conveniently exhibited by dropping them on sugar, and then mixing this thoroughly with water.
The sugar enables the water to hold the oil suspended sufficiently long for use.
A common method of exhibiting the oil is in alcoholic solution, in the shape of spirits or essences. The name spirit, in relation to the aromatic oils, was formerly used to designate preparations made by exposing a mixture of the aromatic and alcohol to distillation; the oil coming over dissolved in the alcohol. It is now also applied to similar preparations, made either by directly dissolving the oil in alcohol, or by distilling the oil and alcohol together. Such is the meaning of the term spirit as employed in the present U. S. Pharmacopoeia, though it is extended so as to embrace spirituous solutions of aeriform or volatile substances in general. But, in former editions of the Pharmacopoeia, to entitle an alcoholic solution of one of the volatile oils to the officinal title of spirit, it was required to be of a strength approaching that of the spirits made in the original method. The name of essences has been popularly appropriated to stronger solutions of the oil in alcohol; generally of such a strength as to permit the preparation to be taken on sugar without further dilution. These were designated in the Pharmacopoeia of 1850 as tinctures of the respective oils. Thus, we had tinctures of the oil of peppermint, and oil of spearmint; but this nomenclature has been abandoned.
Another very common and useful form of exhibition is that of the aromatic waters. These were originally made by distilling water from the aromatic in substance; but this method of preparation has, in the United States, been almost entirely abandoned for the much more convenient method of simply dissolving the oil in water. When the oil and water are merely shaken together, they unite but sparingly, and the resulting solution is very feeble. But, by the intervention of some body which, without being itself soluble, may, by trituration with the oil, so divide; its particles as to bring them into intimate contact with the particles of water, when the two are shaken or rubbed, together, a considerable proportion of the oil is taken up; enough to give a decided odour and taste, and some medicinal activity to the solution. The substance preferred for this purpose is usually carbonate of magnesia; and the aromatic waters of our national standard are prepared in this way; care being always taken to separate the insoluble matter by filtration. The aromatic waters may sometimes be advantageously given with a view simply to the medicinal effect of the oil; but much more frequently they are used as menstrua or vehicles for other substances, the taste of which they cover, while they often render them more acceptable to the stomach.