LABORATORY. A place fitted up and supplied with the necessary apparatus for chemical operations. Laboratories for conducting chemical processes on a large manufacturing scale will of course vary in their arrange ments according to the main object for which they are designed. For experi mental and general purposes a laboratory is more advantageously placed above than below ground, that it may be as dry as possible ; the air must have free access to it ; and it must even be so constructed that, by means of opposite openings, a current of air may be admitted to carry off noxious vapours. A chimney ought to be constructed so high that a person may easily stand under it, and extending the length of one of the side walls. The chimney should be high, and sufficiently contracted to make a draught. When charcoal is the only fuel to be employed no soot wr be deposited, and therefore it need not be so wide as to allow a chimney-sweeper to pass up it Under this chimney may be constructed some brick furnaces, particularly a melting furnace, a furnace for distilling with an alembic, and one or two ovens like those in kitchens. The rest of the space ought to be filled up with stands of different heights, from a foot to a foot and a half, on which portable furnaces of all kinds are to be placed. These furnaces are the most convenient, from the facility of disposing of them at pleasure ; and they are the only furnaces which are necessary in a small laboratory. A double pair of bellows of moderate size must also be placed as commodiously as poesible under or near to the chimney, and having a pipe directed towards the hearth where the forge is to be placed. The necessary furnaces are the simple furnace, for distilling with an alembic, a lamp furnace, two reverberatory furnaces of different sizes for distilling with retorts ; au air or melting furnace, an assay furnace, and a forge furnace. Under the chimney, at a convenient height, should be a row of hooks driven into the back and side walls, upon which are to be hung small shovels, iron pane, tongs, pincers, pokers, and various utensils for disposing the fuel and managing the crucibles. To the walls of the laboratory should be fixed, or suspended, rows of shelves, of different breadths and heights, for containing bottles and glass vessels, which should be as numerous as is possible, that the products of operations may be con veniently retained. The most convenient place for a stone or leaden cistern to
contain water, is a corner of the laboratory, and under it a sink ought to be placed, with a pipe by which the water poured into it may discharge itself. As the vessels are always cleaned under this cistern, cloths and bottle-brushes ought to be hung upon hooka fastened in the walls near it In the middle of the laboratory a large table is to be placed, on which mixtures are to be made, preparations for operations, solutions, precipitations, small filtrations ; in short, whatever does not require fire, excepting that from a lamp. In convenient parts of the laboratory are to be placed blocks of wood upon mats, one of which is to support a middle-sized iron mortar. another a support for a middle-sized marble, or hard stone mortar, and a third for an anviL Near to the mortars are to be hung sieves of different fineness and aizes ; and near to the anvil, files, rasps, pincers, shears, and other convenient utensils for working metals, or giving them proper forms for the several operations ; two movable trestles, to support a large filter or other apparatus, that they may be disposed of conveniently. On account of the dust from charcoal, the stock of this article had better be placed contiguous, but not inside the laboratory ; also some dried furze or other quick burning fuel. In the same place may be put bulky articles, bricks, tiles, clay, lime, sand, and many other things useful iu chemical operations. A small, solid table, for a levigating stone and mailer; small mortars, of iron, glass, agate, and Wedgwood ware ; earthen, stone, metal, and gibs vessels of different kinds ; fun nels, measures, glass-tubes; spatulas of wood, metal, ivory, and glass; pasteboards, writing paper, nuked paper, clean straws, horns, corks, Madders, linen strips, luting., cements, paste, glue, portable bellows, brushes, boxes, &c. &c. are all occasionally wanted in a laboratory. See lire's Dictionary of Chemistry. '