This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
In a general and practical sense, by alcohol is understood the pure spirit obtained by distillation from all liquids which have suffered vinous fermentation. It is the intoxicating principle of all vinous and spirituous liquors. Alcohol is never produced except by the vinous or alcoholic fermentation of particular substances; and after the completion of such action, distillation of the fermented body affords it either in a concentrated or in a diluted state.
Alcohol is also called rectified spirit, spirit of wine, hydrate of ethyl and ethyl alcohol (in opposition to methyl or wood alcohol). Chemically considered, alcohol is an organic compound; it is colorless, transparent, volatile, of penetrating, agreeable odor, and strong burning taste.
The alcoholic or vinous fermentation which starts in the presence of a ferment (yeast) and at a temperature of between 60° and 90° F. is a process which consists in splitting up inverted sugar (grape-sugar) into alcohol and carbonic acid gas, the alcohol being separated by distillation. In the United States, potatoes, corn and the cereals furnish almost the whole of the alcohol found in the market. Cane-sugar is not directly fermentable until it has been inverted, either by the action of a ferment or of a diluted acid.
The fermented juice of the grape is wine, and contains from ten to twelve per cent, alcohol. The fermented juice of the apple, cider; fermented infusion of malt, beer; cider and beer contain from four to six per cent, alcohol. The distilled product of vinous liquors forms the different ardent spirits of commerce. When obtained from wine it is called brandy; from fermented molasses, rum; from cider, malted barley or rye, whisky; from malted barley and rye meal with hops, and rectified from juniper berries, Holland gin; from malted barley, rye or potatoes, and rectified from turpentine, common gin; and from fermented rice, arrack. These spirits, of course, all contain different proportions of alcohol. Their strength is accurately judged by the specific gravity.