BRASS, or LATTEN, a combination of zinc and cop per, is produced by the fusion of the latter metal, and lapis calanzinaris. It is capable of being wrought with great facility, and is applied to a variety of purposes in the arts.
It is of a beautiful yellow colour, more approaching to gold, and not so apt to tarnish or rust as copper. It is more ductile than either that metal or iron, and hence peculiarly fitted to be made into wire. As brass is in general used for mathematical and astronomical instru ments. where the greatest precision is required, its ex pansion has been very accurately determined. It has been found to hold a middle place between its compti neat metals—copper and zinc ; and, according to Mr Smeaton, twelve inches in length of cast brass, at 30", expanded by 180° of heat 225 ten thousandth part of an inch ; while, in the same circumstances, hammered copper expands only 204, and zinc 353 parts. Its den sity is beyond the mean, and ought to be by calculation 7.6296, but is actually 8.3958. See EXPANSION.
This beautiful alloy was known at a very early pe riod. It was first discovered from the singular circum stance of copper ore, and zinc earth, or calamine, some times called cadmift by the ancients, being found in one mine, and yielding, when melted, not pure copper, but metal of a yellow colour ; and from its resemblance to gold, the mines which contained this ore were held in the highest estimation. It was, however, afterwards discovered, that a certain earth, when added to copper, when in the furnace, gave it a gold colour. This earth, which must have been calamine, is mentioned both by Aristotle and Strabo ; and Pliny says, "Ipse lapis, ex zyuo fit es, cadmia vocatur ;" and when speaking of the Marian brass, " floc a Liviano (ere) cadmiam ma rime sorbet."" Its use has been handed down through every century, and is still retained in the manufacture of brass. This discovery was no sooner effected, than the ancient method of procuring this metal was abandoned. Pure copper was first extracted from the ore, and then con verted into brass by the addition of calamine. But as the art of making brass with lapis calaminaris was not well understood by the ancients, but cost them much trouble and expense, it was esteemed next to silver ; and was reckoned little inferior to that metal, as we learn from Procopius, who Says, " that brass, inferior to gold in colour, is almost equal to silver in value."t It was not considered as a distinct metal, but only a more valuable kind of copper ; and hence we find that the *Ford es, which is generally translated brass, was used indifferently to denote either of the two metals. The term orichalcum, however, which is used by Pliny, was more definite ; and 1)1- Watson has very satisfacto rily shewn, that it was confined entirely to brass, while copper was called .rs cyprium, and by later writers cu prum. But the mines which produced the orichalcum of Pliny were exhausted in his time rrperitur longo jam fenzpore, eflieta lellure ;"f as also the Sallus tian mine in Savoy, and the Livian mine in France ; and the best brass then in use, was the Marian, called also a's cordubense, which was found in Spain.
In modern times, considerable improvements have been made in the manufacture of this metal ; and some secrecy is observed by those who have the reputation of making the finest article. This manufacture is carried on in most countries, but no where is brass made more extensively or better than in England, where both the materials are found of the first quality, and in great abundance. The operation of making this metal is very simple, as will appear from the following short descrip tion. The native calamine, after the short process of
calcination, is ground in a mill, and mixed at the same time with about a fourth part of charcoal. This mix ture is put into large cylindrical crucibles, with alter nate layers of copper, cut in small pieces, or in the form of shot. Powdered charcoal is then, thrown over the whole, when the crucibles are covered and luted up. The furnace has the form of a cone, with the base down wards, and the apex cut off horizontally. The cruci bles are placed upon a circular grate, or perforated iron plate, at the bottom, with a sufficient quantity of fuel thrown round them, and a perforated cover, made of bricks or clay, is fitted to the mouth, which serves as a register to regulate the heat. After the copper is sup posed to be sufficiently penetrated with the zinc (the time varying in different works from ten to twenty hours, according to the nature of the calamine, and the size of the crucibles), the heat is increased in order to lose the whole down into one mass, when the crucibles are removed, and the melted brass poured into moulds, and then manufactured in the same way as copper plate. When the materials are good, a single fusion is sufficient to make good malleable brass ; but the finest sorts un dergo a second operation with fresh calamine and char coal. Though the process in all cases is nearly the same, yet there is some variation in the proportion and choice of the ingredients. In this country, the propor tions in weight are about 40 parts of copper, and 60 of calamine, with a sufficient quantity of charcoal ; in Sweden, 40 of copper, 30 of old brass, and 60 of cala mine; in France, 35 of copper, 35 of old brass, 40 of calamine, and from 20 to 25 of charcoal. At Goslar, in Saxony, the cadmia, or sublimed oxide of zinc, is used instead of the native calamine ; and the proportions are 30 parts of copper, from 40 to 45 of cadmia, with dou ble the volume of charcoal.
The use of brass seems to have been very prevalent among the ancients. Most of their arms were compo sed of this metal, as appears from Homer, who in his description of the Greeks, calls them zTotoxi-ra.nEc Ax,cctei , brass coated Greeks ; and we are expressly told by He siod, that brass was in general use before even iron was known.
Most of the arms and instruments found in Her culaneum, Stabea, Pompeia, &c. whether culinary, me chanical, or agricultural, were made of brass, while those of iron were comparatively very few. It may be observed, however, that most of the genuine relics of this kind approach nearer to bronze than to our modern brass, and appear to be composed of various mixtures of brass with tin and other metals.
The Corinthian brass, so famous in antiquity, is a mixture of gold, silver, and copper, and is supposed to have been produced by the fusion of these metals, in which that city abounded, when it was sacked and burned by Lucius Mummius, in the 156th Olympiad, about 146 years before the Christian xra. Of this va luable metal, however, very little is known. Its xra of being in use must have been very short, as we are told by Pliny that the art of making it had been for a long time utterly lost ;* and no remains of it are now in ex istence.
The most celebrated and finest modern brass is made at Geneva. It unites great beauty of colour to a high degree of ductility, and is used chiefly for escapement wheels, and other nicer parts of watchmaking. See Beckmann's History of Inventions, vol. iii. p. 72, &c.; Thompson's Chemistry, vol. i. p. 172 ; Pinkerton's Es say on Medals, vol. i, p. 133 ; Watson's Essays ; and Pliny's Alit. Hist. lib. xxxiv. See also CHEMIS TRY. (L)