Page:Encyclopædia Britannica, Ninth Edition, v. 7.djvu/283

265 DISTILLATION 265 complicated structure. The simple and primitive varieties of apparatus yield only a comparatively weak spirit on the first distillation, while the effect of the complex appliances now generally used is to produce, in one operation ? a highly concentrated spirit, and that with a great saving of fuel, time, and labour. All varieties of distillatory apparatus resolve themsC] ves under these heads : 1st, stills heated and worked by the direct application of the heat of a fire ; 2d, stills worked by the action of steam blown direct into the alcoholic solution from a steam boiler ; and 3d, stills heated by steam passing in coiled pipes through the alcoholic solutions to be acted upon. To the first of these classes stills heated by direct fire belong the earliest and simplest forms of distillatory apparatus ; and for producing particular classes of alcoholic liquor, stills very simple in their construction are yet employed. The common still is a flat-bottomed, close vessel of copper, with a high head to prevent the fluid within boiling over. To the top of this head a tube is connected, which is carried in a spiral form round the inside of a tub or barrel (the condenser or refrigerator), filled with cold water, and from its twisted form this tube receives the name of the &quot; worm.&quot; The tube terminates at the bottom of the barrel, passing through it to the outside, and is con ducted into the vessel termed the receiver, a stopcock, or more commonly a vessel termed a &quot;safe,&quot; being usually placed on the tube where it leaves the refrigerator. In distilling with an apparatus of this simple construction, it is obvious that at the beginning of the operation, when the wash or liquid to be distilled is rich in alcohol, and its boiling point consequently low, the distillate will pass over at a low temperature and contain a high percentage of alcohol. But as the operation progresses, the boiling point of the mixture in the still rises, the heat has therefore to be forced, and the quantity of watery vapour which passes over with the alcohol is proportionately increased. As the wash or liquid in the still continually weakens, a point is arrived at when the value of the weak distillate produced will not balance the expenditure on fuel for maintaining the heat of distillation. One of the earliest devices for economizing the heat of distillation consisted in interposing between the still and the refrigerator a wash warmer, or vessel charged with liquid ready for distillation. Through this vessel the pipe conveying the hot vapours to the refrigerator coil passed, and the vapours, partly condensing there, heated up the wash, which was thus prepared to pass into the still at an elevated temperature. The &quot; pot &quot; stills, in which the markedly flavoured Irish whisky is made, are of this con struction. In the great establishment of the Banagher Distillery Company, King s co., Ireland, simple stills of a capacity of 20,000 gallons are erected having a rousing apparatus within them to keep the wash in agitation so as to prevent solid particles from settling on the bottom and burning. Beyond a wash warmer, or intermediate charger interposed between the still and the condenser, there is no other appliance attached to the apparatus. The first dis tillate from, the still is termed &quot; low wines,&quot; and passes into the &quot;low wines receiver,&quot; whence it passes into No. 1 &quot; low wine still &quot; to undergo a second distillation. The product of the second distillation, under the name of &quot; faints or feints,&quot; is caught in the &quot; faints receiver,&quot; from which it passes to No. 2 low wines still, and from this it is discharged as Irish whisky. The introduction of another principle into distillatory apparatus is illustrated by Dorn s still, which was intro duced into Germany in the early part of the century, and is yet much used in smaller establishments in that country. In that apparatus the vessel, of copper, interposed between the still and the condenser is divided horizontally into two unequal compartments by a diaphragm of copper. The upper and larger portion acts as a wash warmer (German, Vonvarmer), and through it the pipe from, the still body coils, opening into the lower division. For a time the whole distillate condenses in this division, but as the temperature of the wash in the upper division rises, and the heat of the more watery distillate from the still also increases, the condensed liquor in the lower division in its turn begins to boil, and undergoes a second distillation or rectification, the vapours from it passing onwards to be con densed in the ordinary refrigerator. In many forms of distillatory apparatus two or more such rectifiers are placed between the primary still and the final condenser. The principle of the rectifier is easily understood. Supposing the operation of distilling to commence, the vapours which condense in rectifier No. 1 are much richer in alcohol than the liquid remaining in the still. The boiling point of the condensed liquid is consequently proportionately lower, and the vapour from the still passing into it gradually raises it to the boiling point, so that in its turn rectifier No. 1 distills into rectifier No 2 a liquid of still higher alcoholic richness. The relation of No. 2 to No. 1 is the same as that of No. 1 to the still body, and thus the concentration and redis tillation might be carried on to any practicable or desired extent. Another principle brought into play in complex stills for the separation of stronger from weaker alcoholic solutions consists of dephlegmation, or the submitting of the vapour to a temperature so regulated that a portion of it, and that of course the most watery, is condensed and separated, running back into the still or into a special vessel, whilst the richly alcoholic vapour passes on to the rectifier or con denser. In Dorn s still the wide and lofty head attached acts as a dephlegmator, watery vapours condensing on it, and thence falling back into the body ; but in the more recent forms of apparatus such as those of Pistorius and Siemens special dephlegmators of an elaborate nature are introduced. Of the second class of stills those in which the opera tion is conducted by the heat of steam generated in a boiler, and forced into the apparatus the Coffey still may be taken as an example. It is the form most frequently adopted in Great Britain for the manufacture of &quot; silent &quot; spirit, and it is generally recognized as the best and most economical device for preparing a highly concentrated spirit in a single operation. The Coffey still may further be regarded as a type of continuous distilling apparatus, as in it the necessity for withdrawing exhausted solutions and recharging the still with fresh wash is avoided. Beginning, as the Coffey still does, with the steam of pure water, the principle of rectification formerly alluded to is here carried out from the first step. The watery vapour becomes more and more highly charged with alcoholic fumes, till in the end the strongest spirit falls, condensed, into the receiver. In Coffey s apparatus the wash is exposed in a series of shallow chambers, placed one over the other, to the vapour of steam, which rises through the perforated bottoms of each chamber, and carries off the alcoholic vapours into the condenser. This condenser also consists of a series of chambers separated from each other by .per forated plates, and is so contrived that the cold wash passing in pipes through these chambers, in its way to feed the other series of chambers, acts as the condenser to the vapour of the alcohol, the wash being gradually heated thereby, as it passes through the successive chambers. The still, therefore, consists essentially of three separate but connected parts. The first is a large square receiver at the base, which receives the spent wash after it has been deprived of its alcohol by passing through the series of evaporating chambers ; the second, a large, square, upright VTI - 24