However, it is different with a mixture of various vaporizable liquids each of which has a different boiling point. According to the predominance of one or the other liquid the mixture will have a varying boiling point. When the vapors passing over at different intervals are separately condensed it is possible to obtain single components from the mixture, provided, of course, that the various components of the mixture differ decidedly in their boiling points. This special method of distillation is called fractional distillation.
The best-known distillation process is the separation of water and alcohol, or, in other words, the concentration or rectifying of alco holic solutions by means of distillation. This is a special branch of modern industry.
Distillation of The boiling points of water and alcohol differ considerably. At normal atmospheric pressure water boils at 100° C. F.), while alcohol boils at 78.4° C.
(173.5° F.). Consequently, it is evident that the boiling point of a mixture of water and alcohol will range between 173.5° F. and 212° F. In proportion to the predominance of alcohol the boiling point will be lower, and as the alcohol vaporizes the boiling point will rise until, finally, pure water is distilled at 212° F. If a dilute mixture of water and alcohol [the mash in the American distillery usually contains 5 to 10 per cent alcohol by volume (10 to 20 proof)] is dis tilled in a simple distilling apparatus consisting of a pot or still and a worm, dilute alcohol is always obtained, and the smaller the quantity of alcohol contained in the mixture the greater pro portionately will be the amount of alcohol con tained in the distillate, as is shown in the fol lowing table of Groening: is called dephlegination and denotes a draining of the alcohol, as the older chemists designated the water as a component of spirit by the word Another device by which the al coholic vapors are enriched is a small closed retort containing a weak distillate through which the hot vapors are passed. The water vapor is condensed, and the alcohol of the dis tillate vaporizes andjoins the vapors from the still. Accordingly, the more recent apparatus in larger distilleries, in which highly concen trated alcohols are manufactured, are equipped with a dephlegmation and rectification appli ance, in direct connection with the still, so that it has become possible in the column type of still, with continual operation, to produce, from the fermented mash, a high wine free from If the distillate obtained from a dilute mix ture of water and alcohol is redistilled, a dis tillate containing more alcohol is obtained.
Thus in four distillations from a mash having 10 per cent alcohol by volume (20 proof), a raw spirit 80 per cent alcohol by volume (160 proof) is obtained, in which the first distillate contains 28 per cent alcohol by volume, = 56 proof.
second distillate contains 50 per cent alcohol by volume, 100 proof.
third distillate contains 70 per cent alcohol by volume, = 140 proof.
fourth distillate contains 80 per cent alcohol by volume. = 160 proof.
Of course, we assume that each time the dis tillation is carried out completely.
Formerly, it was necessary to repeat the dis tillation several times, in order to obtain a highly concentrated alcohol. The first weak distillate with less than 20 per cent alcohol by volume was called latter. It was used for the further concentration of the alcohol. This method of concentrating alcohol was called doubling or rectification, but as this repetition was tedious and consumed much time and fuel, a shortening of the distillation process was eagerly sought for, and with the aid of suitable appliances it has now become possible to ac complish a complex, separatory distillation in one operation.
The following principle is standard for the construction of distillatory apparatus. If the concentrated alcoholic vapors developed at the boiling of the alcohol-water mixture are not cooled at once to the temperature of condensa tion, but only a few degrees, then a greater part of the less volatile liquid, that is, water, is con densed than of the more volatile alcohol. Through this partial cooling, the remaining vapor accumulates more alcohol. This process fusel, containing 90 to 95 per cent alcohol by volume (180-190 proof).
According to the capacity of the plant, and, especially according to the kind of product, dif ferent types of apparatus are used in the dis tillery; but an enumeration here of these would lead too far, while their description properly be longs under special heads. Therefore only the main types of various distillatory apparatus are mentioned here: 1. Simple stills, with worm condenser heated by direct firing.