DISTILLATION: is, in its fundamental features, the vaporizing of a liquid by heat in one vessel and then conducting the vapor or steam into another cool vessel, where it is condensed into a liquid. The value of the process is found in the fact that very few liquids become vapor at the same temperature. Ethyl alcohol will vaporize at 173° Fahr., and water at 212°—so that each can be readily separated from the other or from other components.
Distillation in its simplest form, may be explained by remarking that if one places a kettle of wine, for example, on a stove, the steam which comes out of the spout prior to the water-boiling point, 212° Fahr., is principally alcoholic vapor, which, if passed into another vessel and held until it condenses into a liquid, will be a crude brandy. A simple distillation will not produce a complete separation—the alcoholic vapor passed out contains a certain percentage of water—but the process can be repeated until nearly all water is eliminated. A complete separation can only be secured by placing the liquid, after distillation to the highest possible percentage, in suspended skin bags. The water, being heavier than the alcohol, settles to the bottom and gradually drips through the bag.
The principal use of the process of distillation is for the manufacture of commercial alcohol (see ALCOHOL) and liquors such as brandy, whisky, rum, etc., and to add special flavors and properties to alcoholic liquors, as in the manufacture of perfumes, liqueurs, etc., but it is also employed to separate light and heavy oils, in the manufac ture of certain products from coal tar, to purify drinking water, to separate volatile from non-volatile substances either in watery or alcoholic solutions or mixtures, etc. Another familiar example is the changing of sea water into fresh water by distillation —the fresh water passes over as steam, leaving the salt behind.
In the manufacture of brandy, rum, whisky, etc., distillation is preceded by other processes which produce a fermented liquid consisting of alcohol, water and solids, it being the duty of distillation to separate the alcohol and water from the solids and then to eliminate a part of the water and certain other volatile substances. Brandy is made from wine (the fermented juice of grapes) ; rum from fermented molasses and other residue of sugar manufacture ; whisky from a fermented grain mixture ( see article on WHISKY) .
The fermented liquid is placed in a "still." The old-fashioned pot-still consists of a large round pot with a short copper "chimney" for the vapor, with a bend at the top and a horizontal continuation in the shape of an elongated neck or spout. The still is
heated to 173° Fahr. and over, by direct fire beneath in a brick "oven" surrounding the "pot," and the alcohol in the ferment changes into vapor or steam and passes up and along the neck. This neck connects with a long tapering copper pipe, called the "worm," coiled in a tank of running water, which cools and condenses the vapor into a liquid and runs it into the receiving vessel. The process is continued until practi cally all of the alcohol contents of the liquor have been extracted. This first product is again distilled and the result is "whisky," "brandy," etc., according to the charac ter of the fermented liquid employed and the method of distillation.
In a majority of present day establishments, large modern stills, the contents heated by steam coils, have succeeded the old-fashioned pot still, but the principle employed is identical.
The still with a short "chimney" leading into the "neck"—in some cases it is only the turn of the neck itself—is employed where it is desired to carry over as much flavor or perfume with the alcohol as possible.
When for other purposes very strong and tasteless spirits are desired, "patent" or high chimney stills are employed, as the flavor-oils, etc., being heavier than the alco holic vapor, fall away in its passage upwards. In addition, three and sometimes four re-distillations are employed to further abstract the water, etc.
Distillation in its leading principles and cruder forms is a process easy of accom plishment, but much care, experience and judgment are required to produce spirits of high grade and quality.