If the vacuum becomes destroyed by the accumulation of the air extricated in boiling, it may be easily restored by refilling 6 as at first. Dr. Arnott states that he planned this arrangement as a simple apparatus for the preparation of medicinal extracts, as many watery extracts from vegetables have their virtues impaired or destroyed by a heat of 212°; but when the water is driven off in vacuo, the temperature need never be higher than blood heat. The doctor further observes, that this plan appears "particularly well suited to the colonies, where air-pumps and nicer machinery can with difficulty be either obtained or managed."

Distillation 409

The annexed engraving represents Sir Anthony Perrier's improved apparatus for distillation. The object of this invention is to cause the liquid to flow gradually over the heated surface of the body of the still, and during its progress to give out its spirituous vapour, and to maintain a continuous and Fig. 2 uninterrupted distillation as long as the supply of liquid is furnished and the fire kept up. Fig. 1 is a view, in profile, of the section of the still, and Fig. 2 is a plan of the same. The bottom of this boiler is divided by concentric partitions, which stand up, as in Fig. l, sufficiently high to prevent the liquor from boiling over. These partitions have openings from one to the other at opposite sides, so as to make the course a sort of labyrinth, f is a reservoir of liquor prepared for the operation; g is a pipe or tube descending from the reservoir, and

Distillation 410Distillation 411

3c conducting the liquor to that part of the boiler marked f f, which is the commencement of the race. From hence the liquor flows through the channels, as shown by the bent arrows, progressively traversing the whole surface of the bottom, whereby the full effect of the fire is exerted upon small portions of the liquid, which causes the evaporation to proceed with great rapidity. The residue of the liquid then passes off by the discharge pipe i, which is made to slide, for the purpose of regulating the quantity and depth of fluid in the still; and this pipe should be in such proportion to the admission pipe, as to cause the perfect distillation of the liquor in its passage to the regulating tube. In the still, as shown at Fig. 1, a set of chains are seen suspended from a bar i i, supported by a centre shaft, which may be put in motion by a toothed wheel and pinion, actuated by a crank or winch. These chains hang in loops, and fall into the spaces between the partitions, for the purpose of sweeping the bottom of the still, and preventing the material operated upon from burning, when of a thick or glutinous nature, as turpentine, syrups, etc.

In the still we are now about to describe, invented by Mr. Frazer, of Houndsditch, the object is the economizing of fuel, and the production of a pure spirit, by a peculiar arrangement of the vessels employed, that shall at the same time be in perfect accordance with the existing excise laws. The wash still, instead of being exposed to naked fire, is immersed in boiling water, the vapour from the former enters the low wine still, where it is condensed; the wine thus abstracts the heat from the wash, becomes itself vapourized, and is conducted into a refrigeratory; the first and second distillations are in this manner conducted together by a continuous process, which will be best understood by a reference to the annexed diagram, a is a supposed steam engine boiler, or other similar vessel, the heat from which boils the wash (or low wine) in the still b. To prevent the liquid from boiling over into the condenser, the neck is formed of the shape shown at i; from hence the vapour passes through a steam-tight case e, immersed in a reservoir c, containing either wash or the product of the first distillation, where it becomes partly condensed; the vapour and condensed liquid then descend through the worm beneath, wherein the condensation is completed and the liquid cooled, which then runs into the closed recipient d underneath.

This recipient d therefore contains the weak spirit of the first distillation, called low wines, to re-distil which product it is raised by the pump f, and discharged into the reservoir c, which is, in effect, the low wine still. The liquid in this vessel, as before mentioned, is vapourized by the heat of the vapour from the wash still passing through it; it is afterwards condensed in the refrigeratory g, and finally received into the closed vessel h, where the operation is completed.

Distillation 412

The engraving on p. 440 represents the patent distilling apparatus of Mr. Stein; in appearance it greatly resembles those constructed in France upon the plan of Woolf s apparatus; but, the principle of its operation is totally different, the object being rather to cause a great economy in the consumption of fuel, than to obtain spirits of any required strength at a single operation. The heat absorbed in the conversion of a given weight of water into steam, exceeds greatly that which is required to raise its temperature to the boiling point; a pound of water converted into steam raising six pounds of water to the point of ebullition. The heat thus developed varies in different liquids, but is in all cases considerable; and as distillation is ordinarily conducted, this heat "s not merely lost, but occasions a considerable additional expense, from the great quantity of water required to reduce the vapour to the liquid state. To obviate these two sources of loss, the patentee has contrived his apparatus, so that one portion of liquid formed into vapour shall be reduced to the liquid form by another portion of liquid, which is evaporated by the heat given out in the condensation.