They are preparations which are obtained by removing from crude drugs a solution of their medicinal principles and evaporating it to the consistence of a soft solid or to dryness. The medicinal principles may be removed either by expressing the crude drugs while fresh and juicy, or by exhausting the dried and powdered drugs with water, alcohol and water, alcohol, or ether, whereby the aqueous, hydro-alcoholic, alcoholic, or ethereal extracts are obtained.

Aqueous Extracts

They were formerly usually made by boiling the drug with water, expressing the watery solution, and evaporating. In nearly all cases infusion or percolation with water has been substituted. The percolate is evaporated to the proper consistency.

Alcoholic Extracts

Whether made with strong or diluted alcohol, the powdered material is most conveniently exhausted by percolation; the alcohol is distilled off from the whole of the tincture, and the residue left is then evaporated to the proper consistence.

Fluid or Liquid Extracts, in the meaning of the United States and British Pharmacopoeias, are permanent concentrated solutions of vegetable drugs, made of such a strength that usually 1 cm. contains the medicinal properties and represents the virtues of 1 gm. of the drug at a temperature of 15° C, (59° F.); Br. 16.5° C. 100 ounces avoirdupois of a drug will practically make 6 pints or 96 fluid ounces of fluid extract. All the fluid extracts are prepared by percolation, and a menstruum uniform in alcoholic strength is employed during the process of exhaustion.

The menstruum for the preparation of extracts to be employed in the manufacture of carbonated beverages is either alcohol, water or glycerine, or a mixture thereof.

The strength or concentration of the commercial extracts is usually weaker, and the bottler may prepare his home-made extract of a strength to suit himself.

We have hereafter - for a uniform rule - directed the exhaustion of le pound of the drug by one pint of liquid, or sufficient to obtain one int of extract. However, for home-use this rule may be altered in some instances where valuable drugs are to be exhausted; in this case enough menstruum may be added to obtain two pints of extract of one pound of drug, but not in all cases is this method recommended, since the alcohol employed for exhausting will also come into consideration as an expensive ingredient.

Compound Fluid Extracts

These are permanent concentrated solutions of additional drugs, made on the same principles.