BRASS, in the arts, a metal much used in various articles of manufacture ; it is compounded of zinc and copper, in the proportion of one part of zinc to three of copper. It is of a fine yellow colour, and more fusible than copper, and less liable to tarnish from exposure to the atmo sphere. It possesses likewise a consider able degree of malleability and ductility, and can be beat into thin leaves, and drawn into fine wire. Its specific gravity is greater than the mean specific gravity of the two metals. See Zssc.
Brass is manufactured in many coun tries; but no where more extensively and better than in England, in which both the materials are in great abundance. The ores of zinc are several species of calamine and of blende, called by the mi ners Black Jack, which are found abun dantly in Devonshire, Derbyshire, and North Wales, generally accompanying lead ores. These are chiefly oxydes, or carbonated oxydes of zinc, and require a previous calcination before they are fit for hrass-making. At Hollywell, in Flintsb ire, the calamine, which is received raw from the mines in the neighbourhood, is first pounded in a stamping-mill, and then washed and sifted in order to separate the lead, with which it is largely admix ed It is then calcined on a broad, shal low, brick hearth, over an oven heated to redness, and frequently stirred for some hours In some places a conical pile is composed of horizontal layers of calamine alternating with layers of charcoal, the whole resting on a layer of wood in large pieces, with sufficient intervals for the draught of air. It is then kindled, and the stack continues to burn till the cala mine is thoroughly calcined. The cala mine, thus prepared, is then ground in a mill, and at the same time mixed with about a third or a fourth part of charcoal, and is then ready for the brass furnace. The brass furnace has the form of the frustrum of a hollow cone, or a cone with the apex cut off horizontally. At the bottom of the furnace is a circular grate, or perforated iron plate, coated with clay and horse dung, to defend it from the ac tion of the fire. The crucibles stand up
on the circular plate, forming a circular row, with one in the middle. The fuel, which in England is coal, is thrown round the crucibles, being let down through the upper opening or smaller end of the cone ; over this opening is a perforated cover, made of fire-bricks and clay, and kept together with bars of iron, so as to fit closely. This cover serves to regulate the heat in the following manner : the draught of air is formed through an un der ground vault to the ash-hole, thence through the grate and round the cru cibles, and through the smaller upper opening into an area where the workmen stand, which is covered by a large dome, and a chimney to convey the smoke into the outer air. When the draught is the strongest, and the heat is required of the greatest intensity, the cover is entirely removed, and the flame then draws through the upper opening of the fur nace to a considerable height into the outer brick dome ; when the heat is to be lessened, the cover is put on, which intercepts more or less of the draught from the furnace, as more or fewer of the holes of the cover are left unstopped. The crucibles are charged with the mix ed calamine and charcoal, together with copper clippings and refuse bits of vari ous kinds, and sometimes brass clippings also, most of which are previously melted, and run into a small sunk cistern of water, through a kind of cullender, which di vides the metal into globules, like shot. Powdered charcoal is put over all, and the crucibles are then covered and luted up with a mixture of clay or loam and horse dung. The time required for heating the crucibles and completing the pro cess, varies considerably in different works, being determined by custom, by the quantity of materials, the size of the crucibles, and especially the nature of the caLmine. In the great way, from 10 to 24 hours are required. At Hollywell, in Flintshire, about twenty-four hours are taken.