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.
Alcohol is the product of a chemical process denominated vinous fermentation, by which, at a temperature between 60° and 90° Fahr., and with the aid of a nitrogenous material called yeast or ferment, sugar, either contained in certain vegetable juices or infusions, or dissolved in water, is converted into alcohol and carbonic acid, the latter of which escapes with effervescence. The liquids thus prepared, containing the newly-formed alcohol, are called fermented liquors. Many of them are employed in medicine, especially wines and malt liquors. When these are submitted to distillation, the alcohol comes over mixed with a considerable proportion of water, and a small proportion of other volatiliza-ble matter contained in the liquid employed. The liquids thus distilled are called ardent spirits, of which there are numerous forms, varying with the character of the fermented liquor from which they are prepared. Among them are brandy, rum, gin, and whisky, all of which are occasionally used in medicine. By subjecting the ardent spirits to another distillation, or as the process has been called, to rectification, the alcohol comes over with much less water, and a smaller amount of other impurity, and now constitutes rectified spirit, or, as it is named in the U. S.
Pharmacopoeia, simply Alcohol. It must be noticed, however, that this is not pure chemical alcohol, but still contains water, and has the sp. gr. 0.835. It is the strongest alcoholic liquid recognized in our officinal code prior to the last revision, when a more concentrated preparation was introduced, with the title of Alcohol Fortius, or Stronger Alcohol, for use in certain pharmaceutical processes. This has the sp. gr. 0.817, and is still far from being pure alcohol; but there is little or no occasion for anything stronger, for the use of the apothecary. As a chemical agent, however, it is sometimes necessary to have a still purer alcohol, which can be procured by further distillation; and, if quicklime be added to the liquid before it is distilled, all the water is retained, and alcohol comes over quite free from that liquid. This is called pure, absolute, or anhydrous alcohol.
Of pure alcohol it is only necessary to say that it is a colourless, volatile, inflammable liquid, of the sp. gr. 0.794 at 60° Fahr., of an agreeable pungent odour, and a burning taste, capable of combining in all proportions with water and ether, and composed of 4 equivalents of carbon, 6 of hydrogen, and 2 of oxygen. The latest view, and the one now generally received, of its precise chemical constitution, is that it is a hydrated oxide of a compound radical called ethyl; in other words, consists of 1 equivalent of ethyl (C4H5) and 1 of oxygen, combined with 1 eq. of water.