BRASS. This very valuable metal is an alloy of copper and zinc, which, from the re motest antiquity, has been extensively applied to useful and ornamental purposes. It was made long before zinc was obtained in its metallic form, by exposing grain or bean copper, which was produced by pouring melted copper into water, or copper clippings, to great heat in crucibles with calcined and powdered calamine, a native carbonate of zinc and charcoal ; but in 1781 James Emerson ob tained a patent for making brass in a more direct way, by melting together its constituent metals ; and this mode is now generally practised. The proportions of the two metals vary much in different kinds of brass, but nearly two-thirds copper and one-third zinc appears to be best for ordinary purposes. M. Maehts, of Vienna, has recently found that brass made in a peculiar way from GO per cent of copper, and 40 of zinc possesses a valuable degree of malleability. Prince's, or Prince Rupert's metal, tombac, or tombak, pinchbeck, similar, Mannheim gold, and se veral other alloys of similar character, are only varieties of brass, the several proportions of which however are variously given by different writers.
The general properties of brass are, a yellow colour, susceptibility of a high polish, and being only superficially acted upon by the air. It is brittle at a high temperature, but very malleable and ductile when cold. Its specific gravity is greater than that deducible from the specific gravities of its constituent metals. It is more fusible, a worse conductor 1 of heat, and harder than copper. The facility 1 with which it may be cast, and turned in a lathe, or otherwise worked, renders it pecu liarly useful in the construction of mathema tical instruments, and the smaller parts of machinery. Brass wire is extensively used in pin-making, and for various other purposes. Lattea is a name sometimes given to thin sheets ofrolledbrass ; and Dutc4 metal or Mack gold is hrass beaten out into very thin leaves.
It has been much contested whether brass is a true chemical compound of copper and zinc, or merely a mechanical mixture. Since the rise of electro-metallurgy, many experi menters have stated that they have precipitated or deposited brass from liquid solution, which, it is calculated, could not occur if the two component metals were merely an alloy, and not a chemical compound. The subject has not yet been definitely settled.
A mode of using sheet brass or other metal for ornamental purposes was introduced a few years ago, in which the appearance of solid metal might be obtained without the weight, by using a wooden core to place the sheet metal upon. The method is useful for making cornice-poles, mouldings, or other articles of continuous form and pattern. The wood is first shaped, by planes and other tools, to the required pattern ; the sheet metal is placed upon it ; and the two together are drawn through a suitable die, which unites them by driving the edges of the metal into the sub. stance of the wood. If the pattern be a plain one, it is struck down upon the wood by the die through which it passes ; but if the pat tern be full and complicated, it is imparted to the sheet metal by swaging tools and dies, previous to the application of the metal to the surface of the wood.
The brass manufacture is one of the most important of the Birmingham branches of industry. No less than thirty manufacturers of that town have announced their intention to present specimens at the forthcoming grand Exhibition, in the departments of brass bed steads, lamps, gas furniture, tubing, orna ments, &c.
Brass work was exported in 1840 to the value of 114,0001.