Page:Encyclopædia Britannica, Ninth Edition, v. 7.djvu/282

264 DISTILLATION non-aerated water from the evaporator pipes, the course of which has already been traced. Here the two products mingle, cool down to the; temperature of the sea, and passing outwards through a filter, may be drawn off as pure aerated water of excellent quality. In Dr Normandy s apparatus the combustion of 1 5) of coal yields from 14 to 20 tt) of potable water. The apparatus is extensively adopted in the British navy, the Cunard line, and many other important emigrant and mercantile lines. Chaplin s apparatus, which was invented and patented later, has also, since 1865, been sanctioned for use on emi grant, troop, and passenger vessels. The apparatus possesses the great merit of simplicity and compactness, in con sequence of which it is comparatively cheap and not liable to derangement. In addition to a boiler for generating steam from sea water the apparatus consists of an aerator, a con denser, and a filter. The condenser is a cylinder, usually of cast iron with an internal worm pipe of copper, which is found to be the only really suitable metal for this use. The steam to be condensed is admitted to this worm or coil through the aerator. This part of the apparatus the aerator is really the essential feature in the invention, and consists simply of a series of holes perforated around the steam inlet pipe at the point where it enters the con denser. The steam passing down in a powerful jet draws with it through these holes a proportion of atmospheric air sufficient to properly aerate the water for drinking purposes. The steam and air thoroughly commingled are together condensed as they pass through the coils of the worm, cold sea water passing in to the condenser at its lowest end, and rising upwards and flowing away at the top. After passing through the filter placed directly under the condenser, the aerated water is delivered or stored ready for use, clear, bright, colourless, palatable, and devoid of odour, at a temperature of about 15 C. The cold sea water for condensing may be forced into the condenser by a special steam pump attached to the apparatus a plan usually followed on sailing vessels or any other convenient pumping arrangement may be resorted to. The steam for condensation is, in steamers, frequently supplied from the engine boilers ; but generally it is preferable to employ a special small upright boiler, or to use the boilers attached to steam winches. Chaplin s apparatus has been adopted by many important British and Continental shipping com panies, among others by the Peninsular and Oriental, the Inman, the North German Lloyd, and the Hamburg American Companies. DISTILLATION OF SPIRITS. Notwithstanding the enormous scale on which this industry is now prosecuted, it is only in modern and comparatively recent times that it has attained to the important position which it now occupies. The art of separating alcoholic spirit from fermented liquors appears, however, to have been known in the far East from the most remote antiquity. It is supposed to have been first known to, and practised by, the Chinese, whence a knowledge of the art gradually travelled westward. A rude kind of still, which is yet employed, has been used for obtaining ardent spirits in Ceylon from time immemorial. The name alcohol indicates that a knowledge of the method of preparing that substance probably came to Western Europe, like much more chemical knowledge, through the Arabs. Albucasis, who lived in the 12th century, is spoken of as the first Western philo sopher who taught the art of distillation as applied to the preparation of spirits ; and in the 13th century Raymond Lully was not only well acquainted with the process, but also knew the method of concentrating it into what he denominated aqua ardens by means of potassic carbonate. At the time when Henry II. in the 12th century invaded and conauered Ireland, the inhabitants were in the habit of making and using an alcoholic liquor usquebagh (uisge-bedtha, water of life), a term since abbreviated into whisky, which consequently is synonymous with the classical aqua vitce. It is further a noticeable fact that Captain Cook found, among the inhabitants of the Pacific Islands discovered by him, a knowledge of- the art of distilling spirit from alcoholic infusions. The preparation of ardent spirit involves two separate series of operations: 1st, the making of an alcoholic solution by means of vinous fermentation ; and 2d, the concentration of the alcoholic solution so obtained by the process of dis tillation and rectification. All substances in nature which contain sugar in any of its forms are susceptible of undergoing vinous fermentation, and may therefore be used as sources of alcohol. Further, all starchy substances and ligneous tissue, seeing that by various chemical processes starch and cellulose may be converted into grape sugar, may also be used for the pre paration of alcohol. It is thus obvious that the variety of organic substances, especially of the vegetable kingdom, from which alcohol may be elaborated is almost endless ; and in practice it is found that the sources employed are very numerous. Commercially, distilled alcoholic liquors are manufactured of varying strength, or proportion of alcohol to water, according as the spirit is intended to be used for drinking purposes or for employment in the arts. The standard by which excise duty on alcoholic liquor is charged in Great Britain is proof spirit, in which the alcohol and water are in almost equal proportions by weight, there being in 100 parts 49 2 4 of absolute alcohol, and 50 76 of water. Distilled spirits are said to be "ovtr proof " when the proportion of alcohol is greater, and " under proof " when there is more water present than is indicated by " proof." Thus a spirit 11 over proof (o.p.) is a compound which requires the addition of 1 1 volumes of water to every hundred to reduce it to proof strength ; and similarly 10 under proof (u.p.) indicates a liquor from every 100 gallons of which 10 gallons of water must be withdrawn to bring it to proof strength. Spirit for drink ing is seldom sold at more than 1 1 over proof, from which it varies downward to 25 and more under proof. Rurn, however, is manufactured and imported as highly concen trated as from 10 to 43 over proof. Spirit of wine as used in the arts must be at least 43 over proof, and generally it is sold at from 54 to 64 over proof. The alcoholic liquors enumerated below are those most commonly distilled for drinking or medicinal purposes. Brandy, when genuine, is a spirit chiefly distilled in France from wine. Rum is made from molasses or treacle, and is distilled in the West Indies, and generally in all countries where the sugar cane is cultivated. From fermented infusions of grain, malted and unmalted, and chiefly from barley, whisky is distilled, and that spirit when " silent " or flavourless is the basis of flavoured spirits, such as gin and factitious or British brandy. Arrack is an Oriental spirit distilled from " toddy," or the fermented juice of certain palm trees, and also from rice, which grain is the source of sak<5, the national spirit of the Japanese. Potato brandy is very extensively prepared from the fecula of potatoes in Germany and Russia, and is a spirit much used for fortifying wines, and for making factitious wine, as well as in the arts. Beet root, carrots, Jerusalem artichokes, and several other saccharine roots are also used for the distilla tion of spirit on a commercial scale. The only example of a spirit drawn from animal sources is the koumiss of the Tartars, which is distilled from the fermented milk of mares. The modifications of stills or of distilling apparatus used in the preparation of alcoholic liquor are exceedingly

numerous, and many of the later inventions are of most