Pharmacy.

Date:
[1835]
Catalogue details

Licence: Public Domain Mark

Credit: Pharmacy. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    1S4 P H A R M A C Y. the upper part of which is drawn out into a short j The diameter of the sand-pot intended to be used chimney a few inches in length ; and the Germans being first taken, six inches must be added to it, for are content with covering them with a flat slab of j the cavity round the pot, and also the length of fire-stone or a large file, leaving small openings at the | two bricks, to allow for the thickness of the sides of corners for the sake of the draught. The furnace for Xhe sand-pot and sand-bath is a very important and useful furnace; but, in the usual way of building such furnaces, they are not only defective and faulty in all the general points before mentioned, but in others also, respecting the proper proportion of this particular kind. This furnace is intended to serve for the sublimation of salts, and distillations of all kinds performed in retorts, as also evaporations from glass or Wedgewood dishes. It heats at the same time, when advantageously constructed, a sand-pot and sand-bath. In the sand-pot any operation may be performed in one retort, where the degree of heat re(juired is from that of boiling oil to the first degree of glowing heat, or what is called red-hot. In general, the retort is sunk in the sand, and even covered with it ; but sometimes only as much sand is put in the pot as will keep the retort steady, and this is called a copella vacua. In the sand-bath may be performed several distil- lations, where different degrees of heat are required, from that of boiling spirits of wine to that of boiling oil, as the bath may be made large enough to con- tain five retorts or other vessels of the same magni- tude, which, by being placed nearer or more remote from the sand-pot, or fixed higher or lower in the sand, may receive the several degrees of heat each shall require. The first step towards making this furnace is to procure a proper sand-pot, and two large plates for forming the sand-bath. The size of the sand-pot must be determined by the magnitude of the retorts, or bodies, intended to be used in it. It must be so proportioned as to hold the retort, and to allow about two inches’ space for the sand to surround it on every side. 'J’he best form of sand-pots is that of a cylinder with a concave bottom, which ought to be made double the thickness of the sides. The common pots are generally made with thin bottoms, which subject them to be very soon worn out, if exposed to a strong heat. The plates for the hath should also be of cast-iron, and must be proportioned to the size and number of retorts, or other vessels, proposed to be worked. They must be long enough to allow at least two inches space betwixt every retort, and two inches and a half betwixt them and the sides of the bath, with the ad- dition of two inches for its bearing on the sides of the hollow it is to cover: the same proportion must be observed for the breadth. They may be as thin as it can be well cast, but care must be taken not to break them in the moving or fixing, which may otherwise very easily happen. A flat ring of iron, of about three inches breadth, and of a proper magnitude to receive the edge of the pot into a proper groove or rabbet made in its own inner edge, should also be provided. Two iron doors, with their proper frames and bars for the ash-hole and fire-place, and also an iron frame or slab and bars for the hole for feeding the fire, with other bars and j)lates for the hollow parts of the furnace, must likewise bj? prepared, according to the general directions above given. When the iron work is thus pre|)ared, the particular mode of constructing the furnace may be thus described. j the furnace. These, being put together, give the dia- meter of the whole furnace. To find the due height, the height of the pot must be first taken ; to which must be added eight inches for the distance betwixt the pot and the surface of the fire when at the highest, six inches for the depth of the fire-place, and e'ght inches for the distance of the bars from the ground of the ash-hole ; with the height of a brick for a course that must be carried over the edge of the pot, which being all put together give the height of the whole furnace from the foundation. A round or square canty must then be made in the ground, on the jilace where the furnace is to be erected. This must be large enough to admit the laying the foundation of the furnace in it, and about eight inches deep, that the bars of the fire-place may lie on a level with the ground, the ash-hole being below it. The reason for making this [»art of the furnace below the ground is to prevent the other parts from rising too high. With respect to the sand-pot, this ' is a great inconvenience to the operator when he has occasion to put a charged retort into the pot; for in doing this he greatly losesjiis command of it, if the pot be placed high. But still greater will the incon- venience be with regard to the sand-bath, which, being of course considerably higher than the sand- pot, requires in this case that the operator should have something to stand upon in order to manage the full retorts set into it ;—an expedient always to be I avoided. ] The ground plan or foundation of the furnace must i be laid in this hole, of dimensions suitable to the diameter, as computed by the rules above given, and carried up of solid brick-work of a cylindrical or square form. But a sufficient area must be left for ( the ash-hole, which must be proportioned by laying the bars fixed in their proper situation, by means of ^ the cross-bearing bars in the ground, in the centre of ' the cylinder, and drawing two lines, begun at the ! furthest cross bar, and continued parallel to the two outermost bars, at the distance of a quarter of an inch from them, to the front of the cylinder. The space so described must be left hollow, and the ash- pit door set in the front. This part of the work may be done with common bricks and coal-ash mortar; but they must be laid solid, that the whole mass may not shrink when the mortar shall be subjected to a great heat. The cylinder of brick-work being thus raised about eight inches high, the bars of the fire- place must be laid over the innermost part ol the vacuity left for the ash-hole; and the stoking-door, with its frame, must be also placed in front of the bars ; but they will not, in this manner of construc- tion, coincide with the interior surface or front wall of the furnace. The biick-work must then be again carried up six inches, in the same manner as before; only it must be made to take proper hold both of the cross-bars of the fire-place and frame of the door. But the courses next the fire must be of Windsor brick, and laid with Windsor loam, or Stourbridge clay. If the heat be intended to be very violent, the joints next the fire should be pointed with the proper fire lute. When the fabric is raised to this height, an iron
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