LABORATORY. 



The second ma)' be provided with the 

 work-bench, hammers, anvil, vice, and 

 other tools, and the different furnaces ; 

 and the shed may be devoted to expe- 

 riments of danger, such as arise from 

 explosions, noxious vapours, and the 

 breaking- of vessels. It will be most 

 convenient that these should be upon the 

 ground floor, to secure the advantage of 

 a ready supply of water or fuel, and other 

 articles of heavy consumption. The first 

 of which articles may be largely wanted, 

 in case of accidental combustion, as well 

 as on common occasions. But it is likewise 

 necessary that the place should be dry, 

 in order that labels may be preserved, 

 and other inconveniences avoided. This is 

 the principal general argument in favour 

 of a laboratory above the ground floor. 



It would carry us too far beyond the 

 limits of our work, if we were to give 

 drawings and descriptions of the great 

 variety of vessels, furnaces, and appara- 

 tus, which have been contrived for gene- 

 ral and particular purposes of chemis- 

 try ; and many of the culinary and do- 

 mestic vessels may also be applied in 

 experimental chemistry. We shall there- 

 fore confine ourselves to a few of the most 

 simple and useful. 



In Plate Laboratory, fig. 1, represents 

 a retort, a, and receiver,* b. These ves- 

 sels are used for distillation. The sub- 

 ject is put into the belly of the retort, a, 

 and exposed to heat, and the volatile pro- 

 ducts pass over into the receiver, b, which 

 may be kept cool by the application of 

 wet cloths, or by immersion in cold 

 water, or otherwise, if needful. The 

 place of junction is secured either by 

 fitting the necks together, by grinding, 

 or by means of a lute, which see far- 

 ther on. At c, in the receiver, is a neck 

 closed by a stopper. Receivers or retorts, 

 With this additional neck, are said to be 

 tubulated. Fig. 2, is an alembic, of which 

 a is the body, b the head, and c the neck. 

 Generally speaking, this is not a very use- 

 ful instrument, In large distillations an 

 alembic or still is used, but the condensa- 

 tion is effected by a spiral pipe, called the 

 worm, which passes through a tub of 

 cold water ; in the use of the alembic, fig. 

 2, the beak is inserted into a receiver. 

 When the volatile product of a body ex- 

 posed to be dried, or to undergo evapo- 

 ration by heat, is not required to be pre- 

 served, the process is performed in an 

 open vessel. 



The application of heat to vessels is 

 made either by naked fire, or by the inter- 

 vention of some heated substance, which 



is then called a bath. Chemical baths are 

 made of sand, or of melted lead, or the 

 fusible metal, or of brine, and very fre- 

 quently of water. The evaporable liquids 

 form a bath which cannot be heated be- 

 yond their respective boiling points ; and 

 the other buths, the most common of 

 which is that of sand, are chiefly valua- 

 ble for giving a regular heat without sud- 

 den changes. 



This last purpose is effected likewise 

 with glass vessels, by coating them with a 

 lute. 



A very great number of furnaces have 

 been constructed for chemical and manu- 

 facturing puposes, for which we must ne- 

 cessarily refer to the extensive works ap- 

 propriated to these objects. The opera- 

 tive chemist may have occasion for them 

 of different sizes and figures. A great 

 deal may be done with the common Ger- 

 man stove, and witli small furnaces made 

 out of black-lead pots. But, in general, 

 the philosophical chemist will be well 

 accommodated with one good furnace, 

 convertible to different uses ; and out of 

 many such we select that of Dr. Black, for 

 its simplicity and efficacy, as described in 

 his lectures. 



PI ate -iron is by far the best material 

 for the outside of an experimental fur- 

 nace, but, as its metal communicates 

 heat very fast, this must be cut off by 

 a proper lute lining. The Doctor so far 

 succeeded in this respect, that his fur- 

 nace though only two inches thick in 

 the middle, will not scorch paper ap- 

 plied to its outside, when it is melting 

 iron within. He adopted the simplest 

 rectilineal shapes, because workmen find 

 great difficulty in executing curved and 

 uncommon forms ; and not one of a score 

 of them will do it with accuracy. In- 

 deed, those highly praised forms seemed 

 to him of very little importance in most 

 cases. 



The body, or fire-place, is the only part 

 of this furnace that requires description ; 

 the ash-pit, with its door and registers 

 and grate, being constructed as in any 

 other furnace. It will be easily under- 

 stood by considering the section repre- 

 sented in fig. 3. 



The base, represented by the dotted 

 line A B C, and the top, K L M, are oval 

 plates of iron, the longer diameter, A C, 

 being to the shorter as three to two 

 nearly. The base and top are equal, so 

 that the sides, K A, M C, are upright, the 

 whole body forming an oval cylinder. 

 D E F, is half of the hole in the bottom, 

 which is occupied by the grate fixed on 



