BRASS is an alloy of copper and zinc, largely used for household furnishings, certain parts of machinery, and other ornamental and useful articles. Technically, the term B. is extended so as to include compounds of copper. and tin, as in brass-ordnance, the brasses or bearings of machinery, etc.; but such alloys of copper and tin, though styled hard B., are more strictly varieties of bronze (q.v.), and the present notice will he confined to the alloys of copper and zinc, or yellow brass. In ancient history, biblical and profane, frequent allusions are made to the employment of B. in the construction of musical instruments, vessels, implements, ornaments, and even gates; but as no men tion is made of its mode of manufacture, or even of its composition, it is doubtful if the B. of the ancients was composed of copper and zinc. In the manufacture of B. on the large scale, two parts by weight of copper to one part of zinc are used, the zinc being one half the weight of the copper; but alloys are made for particular purposes with less or greater proportions of zinc. Thus, where a material of more than ordinary tenacity is required, the zinc is reduced to one fourth the weight of the copper; and where an alloy of a hard and brittle nature, possessing little resisting power, is wished for, the zinc is increased to an amount equal with the copper, or greater. In the manu facture of B., either of two processes may be followed. The direct method is to fuse the zinc in a crucible, and gradually add the copper in pieces. But this process is attended with disadvantage, owing to the volatile and oxidizable nature of zinc. The indirect method of forming B. is that which is generally followed in England and else where, and consists in heating in crucibles or pots a mixture of calamine (carbonate of zinc, ZnOCO,), charcoal, and thin pieces of scrap or grain copper. The calamine (q.v.)
is generally first calcined or roasted, so as to expel any traces of sulphur, then mixed with one fourth of its weight of charcoal, and this mixture introduced into the crucible, after which the metallic copper is diffused through the mixture by being beaten in with hammers or mallets. The proportions employed are 3 parts of the mixture of calamine and charcoal to 2 parts of copper; and when introduced into a furnace, and subjected for 5 to 24 hours to the action of a white heat, the charcoal reduces the calamine and separates the zinc, which, combining with the copper, forms 3 parts of B., containing about 2 of copper to 1 of zinc.
For ordinary purposes, B. is first cast into plates of about 100 lbs. weight, and i to in. thick, which can be readily broken up, remelted, and cast in a mold of any desir able shape or size. The crude casting so obtained is generally screwed to a turning lathe, and turned and bored into the required form with iron tools. 13. is very largely employed in the construction of door-handles, window-shutter knobs, etc.; and since the introduction of gas, though the brazen candlesticks have almost ceased to exist in towns, yet the immense number of stop-cocks and brass pendants and brackets required, has given a considerable impetus to the brass manufacture. The proportion of copper and zinc in the alloys resembling B., and which are known as gilding metal, Mannheim gold, pinchbeck, bath metal, Bristol brass, Nunez sheathing metal, spelter, solder, and Mosaic gold, have already been noticed under Alloy (q.v.).