The top of the boiler, which is covered, and well sol, dered, has a neck three or four inches high, and three in diameter; through which the vapour passes, and is received in a small chimney, in the form of a funnel reversed, the upper end of which, of a square figure, con nects with the flue, and conducts the prejudicial vapours into it,

On one of the sides of the boiler is placed a tube C, like the case of an areometer, about a foot long, which, by means of the small communication D towards the bottom, receives the liquid from the interior. In this tube is put a small bottle, in the cork of which is fixed a wire E, which indicates the diminution of the fluid by descending with it. The fluid should never be suffered to fall lower than the top of the box, fixed in the flue of the stove, for fear the solder should melt, and the wire should be placed in such a manner that when it descends to the level of the tube F, it should indicate the diminution of the fluid to the level of the box, and the necessity of adding more water. This small lateral tube terminating in a funnel, is very convenient for replenishing, and even if it be uncovered it emits no kind of smell.

This boiler contains about six quarts; yet it can be employed only for the preparation of 11⁄2 lb. of opium instead of 3 lbs. according to the formula in Baumé's Elements of Pharmacy, which must be followed in other respects; and if one winter is not sufficient for this prepa ́ration, nothing prevents its being interrupted and resumed the following winter, as is my present practice. A vacancy of a few inches should be left for ebullition, and it is better for the top to be of a wider diameter, to prevent boiling over. The ebullition may be moderated

at

at pleasure, by gradually removing the boiler from the flue by which it is heated.

By altering the proportions and form of this machine, it may be employed for many purposes beneficial to society and the arts, with singular advantage in point of economy.

Method of correcting some Inconveniencies arising from the Inequality of the Fire in Distillation on a large Scale. By M. EDELCRantz,

With a Plate.

From the ANNALES DE CHIMIE.

DISTILLATION, as is well known, consists princi

pally of two operations; the conversion of the material to be distilled into vapour by means of fire, and the condensation of this vapour by cold. That this two-fold object may be accomplished with expedition, and without unnecessary consumption of fuel, it is requisite to establish a perfect equilibrium between the vaporising heat and the condensing cold: that is, by supposing the latter constant, as it may be made in practice (a given quantity of water, of a fixed temperature, passing in a determined time through the refrigerant). The fire should be regulated in such a manner that the quantity of vapours produced should be neither greater nor less than what can in the same space of time be condensed by the cold applied. The want of attention to this circumstance, particularly in the distillation of spirits, produces the two following inconveniencies:

1. If the fire is too strong, a great portion of the condensed vapours passes from the worm into the external air, which occasions a loss of the distilled matter and of fuel.

2. If the fire gets too low, the condensation produces a void in the worm and in the still, which not being filled in the same proportion by fresh vapour, obliges the external air to enter, by which the vaporisation and con densation are rendered difficult: and when that air is again forced out, it carries with it part of the vapour, and occasions a loss of the distilled matter and of time.

To remedy these defects, and at the same time to furnish a simple method of indicating at every moment the actual state of the fire, I contrived an instrument which may be adapted to every apparatus for distilling, and which is nothing more than an application of theoretical principles already known.

worm.

Fig. 1, (Plate XIX.) a, b, c, d, is a curved copper or glass tube, in several pieces with a ball b; the upper end of the tube a may be attached by means of a screw to the The length bc, cd, is four feet, and the capacity of the ball b is somewhat greater than the whole capacity of the tube b cd. When the distillation is going on, the condensed vapours will pass through a and the ball b into the tube b cd; and the liquor will not run out at d into a vessel placed to receive it, till the two arms are filled. Thus these two arms will remain full during the whole time of distillation, and in this circumstance consists the remedy to the above-mentioned inconveniences. It is obvious, that if the fire be too violent, the vapour not condensed cannot be dissipated by opening a passage into the external air before it has expelled all the liquor contained in the tube bc, and overcome the pressure of Nnn a column,

VOL. II.

SECOND SERIES.