Half way between i and the end proper of the worm, the pipe is tapped, and a branch, carrying the faucet l, leads into the still m, where it terminates under the centre of the head in the shape of an go, forming a trap to prevent the escape of vapours by this passage. The object of this arrangement is to cause the condensed liquid to flow back into the still as long as the faucet / is open, or to collect it outside by turning off the faucet l. Prolonged digestions with alcohol may be made by means of this apparatus, without any loss of liquid. The head is attached to the still by means of a rubber washer and iron clamps, and when it is desired to remove it, the water is allowed to drain from the condenser, the clamps are removed, and the whole is hoisted up by the tackle n and 'set on one side.
To illustrate the use of the faucet l by an example, we will suppose that we have to completely exhaust 10 lb. of powdered mix vomica. Into a frame fitting into the upper part of the inside of the still is fitted a broad, short, copper percolator, which is packed with the powdered mix vomica. The head and condenser being connected with the still, about 3 gal. of alcohol are poured into the still, and the water having been turned on the condenser, and flowing briskly, steam is carefully turned on at a. The faucet I is kept closed as yet, and the pipe k is made to point into a receiver. As soon as condensed alcohol flows into the latter in a steady and uniform stream, the faucet l is opened, when the flow of alcohol returns to the still, and empties itself from the end of the co over the centre of the percolator. From time to time the faucet is closed, and the regularity of the flow is observed, as it empties itself into the receiver. After a certain lapse of time, depending upon various circumstances, and mainly upon previous experience - in the present instance, after about 4 hours - the nux vomica is completely exhausted, and the last part of the operation consists in turning off the faucet, and permitting all the alcohol to run into the receiver.
Rice is in the habit, when using the apparatus for such purposes, of placing in the still 2 gal. of ordinary glycerine, and in this a large porcelain pot, supported in such a manner that the glycerine surrounds it on all sides up to within about 4 in. of the top. The liquid to be distilled, such as alcohol, is placed in the dish, the distillate, if required to be used as a continuous menstruum, is made to run back into the still, where it flows into the dish, and finally, after distilling off the alcohol, the dish is removed with the extract contained in it. If the tincture is allowed to run directly into the still, and the alcohol is distilled off, it requires considerable labour and waste of alcohol to remove the extract, besides incurring the danger of overheating and almost baking it.
In all cases, when possible, it is recommended to place in the still a pre liminary charge of water, say 1/2-l gal., and to distil this over to dryness. The packing thereby swells up and becomes tight, so that when the alcoholic liquid is introduced no loss will be incurred.
The apparatus is not patented, and Rice places it at the disposal of any one who wants to use it. (New Remedies.)
An improvement on Liebig's condenser is proposed by Abraham. In the old form, the water, heated by vapour in the coil, very slowly rises upwards, mixing at the same time with the surrounding water and producing a large quantity of warm water, which has to be removed to keep the coil cool. In a properly constructed Liebig's condenser, however, a rapid current of water should drive that, in front of it farther and farther without materially mixing with it, until at last it is driven out at a very high temperature, having done all, or nearly all the work it possibly could. In Fig 105, the dimensionscondensers; I, hot-water exit; m, stopcock, with index to regulate flow of water. In designing his new condenser Abraham went on this principle, and not only had his outer or cooling tube as small as possible, but, to further increase its condensing powers, had a thick copper wire wound spirally round the inner tube so as to compel the water to rotate at a high speed. Diameter of internal tube, 1 in.; diameter of external tube, 1 1/2 in.; both No. 16 wire gauge copper tubing.
The old coil was only capable of condensing 4 gal. per hour, and did not always cool that quantity as completely as is desirable for the purpose of distillation in sacuo; in order to ensure against possible failure, and to increase if possible the condensing power, the new one was made, if anything, slightly longer than the old. The efficiency of this condenser is such that it would, if only half its present length, condense and cool perfectly about 6 gal. of liquid per hour. Not only is its condensing power highly satisfactory, but it occupies next to no space, as it is fixed to the wall; it is more cleanly and, what is perhaps of more advantage than anything else, It is very easily cleaned by driving steam through it, whereas a tube requires to be emptied before this can be done.
The wet distillation of camphor is an instance of the adaption of this process for extracting organic products. The most general arrangement of the still and condenser, adopted in the Tosa district of Japan is shown in Fig. 106. On a small circular stone wall A, serving to form a fire-place, lies an iron plate F, 2 1/2 in. thick.
This is covered by a numerously perforated lid, luted tightly with clay, which at the same time forms the bottom E of the vessel h, which is 3 ft. i in. high, and 18 in. wide at the top. Near the bottom is a square opening p, which may be closed by a board. The whole is clothed with a thick coating of clay C, held fast by a binding of bamboo hoops a. The upper opening is closed by a clay-luted oarer 0, having a hole in the centre, furnished with a cork K. Just under this cover, a hollow bamboo stem leaves the still and passes to the box open beneath, divided into 5 inter-communicating compartments by means of 4 partitions and turned with its open side into a vessel M containing water. This condenser is kept con-stantly cool by a stream of water, led over the top by means of the pipe b. The distillation is conducted in the following way. After removing the cover G, the vessel B is filled with the chips of camphor wood, the cover is replaced and well luted with clay; then through the opening k, a certain quantity or water is run in, which, after saturating the chips, will collect in the panF. Gentle firing is now commenced, and is continued for 12 hours, so as to keep the water in F at a steady boil.