a form of still, of common use in our laboratories, for distilling water. The kettle a, which contains the water, is covered by the movable dome в, from which the pipe b c conducts the vapour into the receiver R, which is surrounded with cold water. Thence the condensed liquid descends through a continuation of the tube, bent spirally, called the worm, by which it is exposed to the prolonged action of the cold water, till at length it flows quite cool into the bottle placed to receive it. Into the worm-tub a stream of cold water constantly enters by the pipe p p, while a similar stream of warm water as constantly escapes by the pipe q.

Arrangements somewhat different are made in the large distilleries, chiefly with the view of economising time and fuel. The following (fig. 55) represents a common form of

pparatus, where the process of spirit-distillation is conducted on a large scale. The principal peculiarities in this are -first, The broad flat bottom of the pot or still a, by which the effect of the heat is more quickly and fully obtained;

PROCESS OF DISTILLATION.

277

and, second, The adoption of two worms, в and c, in different vessels. In the first of these vessels cold wort is put, which is heated by the vapours as the distillation proceeds, and when hot is run at once by the stopcock s into the still. The second vessel contains cold water as before, and as this water heats it is run off, and is employed in mashing the grain. Thus heat is economised in various ways.

The spirit which passes off and condenses in the worm is more or less mixed with water, but by means of successive distillations-or rectifications, as they are called-it may be obtained quite free from water. It is then what chemists call absolute alcohol. This pure or absolute alcohol has a peculiar penetrating smell; a hot, fiery, and burning taste; is about one-fifth part lighter than water; * burns readily, but with a pale flame when kindled in the air, and is intoxicating in a high degree. It is used only for chemical purposes. The spirit-of-wine, or common alcohol of the shops, which we burn in our lamps, and employ for other familiar uses, is already diluted with a considerable proportion of water.

In the brandies, or varieties of ardent spirits which we consume as exhilarating drinks, the alcohol is still further diluted with water.

Thus the proportions of alcohol per cent., in some of the common varieties of commercial spirits, are as follows (at 62° Fahr.):

* A vessel which will hold 1000 grains of water will hold only 792 of absolute alcohol. Its specific gravity is therefore said to be 792, that of water being 1000-or 0.792, that of water being 1.

So that on an average, we may say that the ardent spirits we consume contain only half their weight, or three-fifths of their bulk of absolute alcohol. They are about twice as strong as our port, sherry, and Madeira wines.

Every different fermented liquor, when distilled, yields an ardent spirit which has a flavour, and is generally distinguished by a name of its own. Thus wine yields what we call brandy or cognac: fermented molasses yields rum; Indian corn, potatoes, and rye, yield liquors which are distinguished as corn, rye, and potato brandies; while malt. liquors give our Scotch and Irish whiskies. If juniper berries be added previous to distillation, as is usually done in Holland, a flavour is imparted to the spirit which is characteristic of gin or Hollands; and if the malt be dried over a peat fire, the smell and taste of the peat (the peet-reek) accompany the spirit prepared from it; and these, in the estimation of the initiated, impart a peculiar value to peet-reek whisky.

2o. THE DISTILLERS' PROCESSES.-But though malt and other liquors, fermented in the usual way—indeed, in almost any way-will yield brandy by distillation, yet the distiller by profession conducts his fermenting operations in a somewhat different way from the brewer, whose object is merely the production of beer. Thus

First, We have seen that, in fermenting the wort for the manufacture of beer, a large proportion of the sugar is left in the liquor unchanged. The fermentation is stopped before this sugar is transformed into alcohol, in order that the beer may be pleasant to drink, and that it may keep in the cask without turning sour. But the distiller's object is to obtain the largest possible quantity of spirit from his grain; he therefore prolongs the fermentation until the whole of the sugar is transformed, as nearly as possible, into alcohol and carbonic acid. To leave any of it unchanged

USE OF UNMALTED GRAIN.

279

would not only involve a loss of spirit, but, during the subsequent distillation, might injure the flavour and general quality of the spirit he obtained. The securing of this point, therefore, requires on his part an attention to minute circumstances, different a little in kind, but not less nice and delicate than those which determine the success of the brewer's operations.

Again, the most agreeable and generally esteemed grainspirit is obtained when malted barley only is employed in the manufacture. This yields in Scotland and Ireland the best malt whisky. The profit of the distiller, however, is often promoted by mixing with the malt a greater or less proportion of unmalted grain, or even of potato starch. To the reason of this I have already briefly alluded (p. 243), but it is worthy of a fuller explanation.

We have seen that it is the diastase, produced during the germination of the barley, which subsequently transforms the starch of the grain into sugar. This diastase is capable of so transforming nearly a thousand times its own weight of starch; but good malt contains only a hundred of starch to one of diastase. The latter ingredient, therefore, will transform into sugar ten times as much starch as it is associated with in the best malt. Hence a large quantity of starch, either in the form of crushed unmalted grain, or of potato starch, may be mixed even with ordinary malt in the mash tub, with the certainty that the diastase of the malt will transform it all into sugar.

This is what the distiller does in making grain whisky; and the profit of it consists in this--that he saves both the expense of malting his grain and the loss of matter (usually 8 per cent.), which barley always undergoes in malting.

* A hundred pounds of barley yield only eighty pounds of malt. But of this loss 12 per cent. consists of water driven off by the heat of the malt kiln, so that the real loss of substance is 8 lb. in the 100.

He is able, also, to use for these additions of grain an inferior or cheaper material than is usually employed for conversion into malt.* The sweet wort obtained in this way, when fermented and distilled, yields a spirit of a somewhat harsher and less pleasant flavour than when malt alone is used.

Along with the spirit, during the distillation of fermented liquors, there always passes over a small but variable proportion of one or more volatile oily liquids, which mix with the spirit and give it a peculiar flavour. These volatile oils vary in kind, in composition, and in sensible properties, with the source of the sugar which has been submitted to fermentation, and with the substances which are present along with it in the wort. Hence the spirit obtained from almost every different fermented liquor is distinguished by its own characteristic flavour. Thus wine, brandy, or cognac, derives its vinous flavour from the juice of the grape; and cognacs of different districts their special flavours from the kinds of wine which are distilled in each. Rum obtains its smell and taste from molasses, the scorched and altered juice of the sugar cane; whisky its peculiarities from the barley-malt or grain that is mixed with it; potato brandy, from the mashed potato or its skin;† palm brandy,

*Thus, in some of the Scotch distilleries, such a mixture as the following is employed:

The diastase in the 42 bushels of inalt converts into sugar the starch of the whole 250 bushels, weighing eight times as much as the malt itself. This quantity of grain yields on an average 583 gallons of proof whisky, or 14 gallons from 6 bushels of the mixture.

Potato brandy is contaminated, among other substances, by a volatilo spirit called amyle alcohol. And it is a singular circumstance that the cognac distilled in the south of France from the grape husks-known as Eau de vie de marc de raisinalso contains the same amyle alcohol. In the one case it is probably derived from the skin of the root, in the other from the skin of the fruit.