The operation of distilling is often carried on in the apparatus represented in Fig. 111. It is termed the Patent Simplified Distilling Apparatus; it was originally invented by Corty, but it has since undergone much improvement. A is the body of the still, into which the wash is put; B, the head of the still; c, 3 copper plates fitted upon the upper part of the 3 boxes; these are kept cool by a supply of water from the pipe £, which is distributed by means of the pipes 6. The least pure portion of the ascending vapours is condensed as it reaches the lowest plate, and falls back, and the next portion as it reaches the second plate, while the purest and lightest vapours pass over the gooseneck, and are condensed in the worm.
The temperature of the plates is regulated by altering the flow of water by means of the cock F. For the purpose of cleaning the apparatus, a jet of steam or water may be introduced at a. A gas apparatus is affixed at the screwjoint H, at the lower end of the worm. The part of the apparatus marked I becomes filled soon after the operation has commenced: the end of the other pipe K is immersed in water in the vessel L. The advantage claimed for this apparatus is that the condensation proceeds in a partial vacuum, and that there is therefore a great saving in fuel. One of these stills, having a capacity of 400 gal., is said to work off 4 or 5 charges during a day of 12 hours, furnishing a spirit 35 per cent. over-proof. Fig. 112 represents a double still which is largely employed in the colonies. It is simply an addition of the common still A to the patent still B. From time to time the contents of B are run off into A, those of A being drawn off as dunder, the spirit from A passing over into B. Both stills are heated by the same fire; and it is said that much fine spirit can be obtained by their use at the expense of a very inconsiderable amount of fuel.
In Jamaica, however, nothing is likely to supersede the common still and double retorts, shown in Fig. 113. It is usually the custom to pass the tube from the secona retort through a charger containing wash, by which means the latter is heated previous to being introduced into the still; the tube then proceeds directly to the worm-tank. With an arrangement of this kind, a still holding 1000 gal. should produce 500 gal. of rum (30-40 per cent. over-proof), between the hours of 5 in the morning and 8 in the evening. The first gallon of spirit obtained is termed "low wines," and is used for charging the retorts, each of which contains 15-20 gal. After this, rum of 40-45 per cent. over-proof flows into clean cans or other vessels placed to receive it.
The apparatus used in England for the distillation of grain-spirit is known as "Coffey's" still; and is shown in Fig. 114. It consists of 2 columns, CDEF and GHJK, placed side by 6ide, and above a rectangular chamber, containing a steam-pipe b from the boiler A. This chamber is divided into 2 compartments by a horizontal partition, pierced with small holes, and furnished with 4 safety-valves e. The column CDEF, called the analyser, is divided into 12 small compartments, by means of horizontal partitions similar to the one beneath, also pierced with holes and each provided with 2 little valves f. The spirituous vapours passing up this column are led by a pipe to the bottom of the second column or rectifier. This column is also divided into compartments in precisely the same way, except that there are 15 of them, the 10 lowest being separated by the partitions A, which are pierced with holes. The remaining 5 partitions are not perforated, but have a wide opening as at w, for the passage of the vapours. Between each of these partitions passes one bend of a long zigzag pipe m, beginning at the top of the column, winding downwards to the bottom, and finally passing upwards again to the top of the other column, so as to discharge its contents into the highest compartment.
The apparatus works in the following way: - The pump Q is set in motion, and the zigzag pipe then fills with the wash or fermented liquor until it runs over at n'. The pump is then stopped, and steam is introduced through b, passing up through the 2 bottom chambers and the short pipe z into the analysing column CDEF, finally reaching the bottom of the other column by means of the pipe i. Here it surrounds the coil pipe containing the wash, so that the latter becomes rapidly heated. When several bends of the pipe have become heated, the pump is again set to work, and the hot wash is driven rapidly through the coil and into the analyser at n'.Here it takes the course indicated by the arrows, running down from chamber to chamber until it reaches the bottom; none of the liquor finds its way through the perforations in the various partitions, owing to the pressure of the ascending steam. In its course downwards the wash is met by the steam, and the whole of the spirit which it contains is thus converted into vapour.
As soon as the chamber B' is nearly full of the spent wash, its contents are run off into the tower compartment'by opening a valve in the pipe V. By means of the cock N, they are finally discharged from the apparatus. This process is continued until nil the wash has been pumped through.
The course taken by the steam will be readily understood by a glance at the figure. When it has passed through each of the chambers of the analyser, the mixed vapours of water and spirit pass through the pipe i into the rectifying column. Ascending again, they heat the coiled pipe m, and are partially deprived of aqueous vapours by condensation. Being thus gradually concentrated, by the time they reach the opening at W they consist of nearly pure spirit, and are then condensed by the cool liquid in the pipe falling upon the partition s, and being carried away by the pipe y to a refrigerator. Any un-condensed gases pass out by the pipe R to the same refrigerator, where they are deprived of any alcohol they may contain. The weak liquor condensed in the different compartments of the rectifier descends in the same manner as the wash descends in the other column; as it always contains a little spirit, it is conveyed by means of the pipe S to the vessel L in order to be pumped once more through the apparatus.
Before the process of distillation commences, it is usual, especially when the common Scotch stills are employed, to add about 1 lb. of soap to the contents of the still for every 100 gal. of wash. This is done in order to prevent the liquid from boiling over, which object is attained in the following way: - The fermented wash always contains small quantities of acetic acid; this acts upon the soap, liberating an oily compound which floats upon the surface. The bubbles of gas as they rise from the body of the liquid are broken by this layer of oil, and hence the violence of the ebullition is considerably checked. Butter is sometimes employed for the same purpose.
When the still contains a charge of about 8000 gal., distillation is carried on as quickly as possible until about 2400 gal. have passed over. This portion possesses but little strength, and is known as " low wines." The remainder of the 8000 gal. is received in another vessel for re-distillation, and the low wines are also re-distilled in another still, until the product acquires an unpleasant taste and smell; these, which are then called "faints," are collected in a vat called the "faints back," mixed with the impure portions of the first distillation, diluted with water, and re-distilled. The product of a further distillation then yields finished spirit.
Fig. 115 represents the apparatus used in Neufehatel and other places for the manufacture of absinth and similar perfumed spirits. It consists of the following parts: -
A is a kettle enclosed in a wooden jacket, acting as a water-bath enclosing another kettle, which contains the ingredients to be distilled. B is the top or cover of the still; C an opening closed by a plug for charging the still; C a similar opening for discharging the plants after distillation. D is the cap of the still, fastened on by a circular collar, and terminating in a neck which conducts the alcoholic vapours to the cooling coil. £ is the cooler with its coil, and E' the discharge pipe of the coil. F is the colourer, furnished, like the still, with plugs through which to fill and empty it. G is a pump fastened firmly to the wall by the collars 6'. H is a piston rod; I, the eccentric for driving the pump; J, a pulley on which a band runs to connect with the power; and K, bearings from the pulley shaft. L is a tank or well of metal sunk into the floor. M is a suction pipe, and M' another, connected with the colourer. N is a 3-way cock attached to the suction pipe to draw any liquid from the tank to deliver it into the still, into the colourer, or to the store-room, or to draw the finished liquor from the colourer, and deliver it to the store-room. N' is a pipe for drawing off the coloured product; O is a force or delivery pipe; P, a 3-way cock, which directs liquids at pleasure into the still or the colourer; P', a pipe delivering the liquid into the colourer, and P" a pipe conveying the liquor into the still.
R is a cock and pipe for delivering the manufactured product into the store-room; S, a funnel and pipe to convey the distilled product to the tank; T, the main steam-pipe connected With the steam boiler; U, the steatn-cock for the kettle of the still; and V the steam-cock for the colourer.
The Apparatus is worked in the following manner: - The tank L having been tilled with tank is empty, the pump is stopped and the cock P closed. Steam is turned on by opening the cock U, and the product soon begins to flow over from the condensing coil into S, and again fills the tank L; it now consists of spirits perfumed by the plants placed in the still; it is white in colour, and possesses already many of the properties peculiar to the manufactured article. In order to colour it, the pump again draws up the liquor into the colourer P, which has been previously filled with the proper quantity of the colouring plants. After this operation, the pump fulfils its third office by raising the coloured absinth from the colourer through the pipe N', and the cock and pipe R into its final receptacles.