when the thermometer approaches 212° F. (100° C.) and the taste and smell of the liquid distilling over (distillate) indicate the presence of very little alcohol.

Where such an apparatus as that just described is not to be obtained, some simpler contrivance must be substituted for it.

A plain retort (a, fig. 60) with a long neck may be employed, and any common bottle (b) will serve for a receiver.

FIG. 61.

Distillation.

To promote condensation, a long strip of filter-paper (c) may be wetted and wrapped smoothly round the neck, a string of wet tow (d) being passed twice round the neck at the lower edge of the paper, and twisted tightly into a tail to carry off the water, which may either be gently poured from time to time upon the upper part of the paper, or allowed to trickle slowly from a funnel (e), the neck of which is partly stopped with tow. A tube funnel (fig. 61) is employed for introducing the liquid into the retort without soiling the neck.

funuel.

A flask with a bent tube (229), tightly fitted into it with a perforated cork (228), may be employed Tube, instead of a retort. One limb of this tube may be 20 or 30 inches long, to insure condensation, or it may be adapted, either by a perforated cork or a caoutchouc bandage, to a wider tube of considerable length (fig. 62). A convenient support for this tube is made by fixing a per

TO PERFORATE CORKS.

171

forated bung into the ring of a retort-stand turned round into the required position.

FIG. 62.

Distillation in a flask.

228. To perforate corks.-Smooth cylindrical holes are made in corks with rat's-tail files (fig. 63), beginning with a

FIG. 63.

Rat's-tail file.

small size, and employing the larger files as may be necessary. Corks should always be kept on the points of the files when not in use, as the steel is

very

brittle.

FIG. 64.

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A set of brass cork borers of various sizes (fig. 65) will save much time. They are made to slip CCC into each other, and are provided with a steel rod (fig. 64) which

FIG. 65.

Set of cork-borers.

serves as a handle and for thrusting out the cylinders of cork

punched by the borers.

what less diameter than the tube for which the hole is to be bored, and the rod is thrust through the holes in the head of the borer. The cork is held firmly against the wall or the

A cork-borer is selected of some

edge of a table (fig. 66),

Boring a cork.

and the borer worked straight into it, like a gimlet, until it is about half way through the cork. The borer being withdrawn, and cleared, if necessary, with the rod, the cork is reversed, and bored in the opposite direction, so that the two holes may meet in the centre, and form a perfectly smooth cylindrical passage, which is very carefully enlarged with a rat's-tail file until it is just large enough to receive the tube, which should pass through it with considerable friction.

In fitting corks air-tight they should be carefully selected as free from flaws as possible, especially at the ends. The cork should be somewhat too large to enter the mouth of the vessel until it has been softened by rolling it heavily on the table with the palm of the hand, or, in the case of large corks, under the sole of the boot. Corks are always to be preferred to bungs or shives.

Vulcanized India-rubber stoppers are often substituted for corks, and are decidedly preferable in a great many cases. They may be perforated with the cork-borers described above, which should be dipped in spirit of wine.

229. To bend glass tubes.-Small tubing may be bent

FIG. 67.

Bending glass tube.

either in the flame of a spirit-lamp, or in the upper part of a somewhat flaring gasflame (fig. 67). The tube should be slowly rotated, and moved to and fro in the flame until soft enough to be bent, which should be effected by a gentle equal pressure with both hands, care being taken so to regulate the soft

SPIRIT BLOWPIPE.

ening of the glass as to obtain a nice curve (fig. 68) instead of a sharp angle (fig. 69). Any soot which has been deposited from the flame may be wiped off with paper when the tube is cool.

Large tubing is more difficult to bend, and it is often necessary to employ a blowpipe flame.

FIG. 68.

FIG. 69.

173

The bend must be annealed by

withdrawing it very gradually from the heat.

convenient

The gas blowpipe represented in fig. 70 is very for such purposes, especially if connected with a double-action bellows worked by the foot.

Where gas is not to be had, a spirit blowpipe-lamp is sometimes used. That represented in fig. 71 answers the purpose very well. A small quantity of spirit (either methylated spirit of wine or wood-naphtha) burnt inside the vessel a vaporizes the spirit in the space b between the walls; the vapor issuing from the jet c, burns with a powerful flame. These lamps are not free from danger in consequence of a particle of cork getting into the spirit and obstructing the