Zinc readily unites with copper; and the usual manner of forming brass by brass-founders, is to make a direct union between the two metals. The process, however, generally consists in mixing together granulated copper, calamine, or carbonated oxide of zinc, and charcoal in powder, and melting them in a crucible. The charcoal reduces the zinc, which then unites with the copper. The heat is kept up for five or six hours, and towards the last of the process, is raised. Zinc, in small proportion, renders copper pale, and in the proportion of one-twelfth, inclines its colour to yellow. The yellow colour increases in intensity with the zinc, until the weight of this metal in the alloy equals that of the copper. An increase of zinc, afterwards makes the alloy white. English brass contains one-third of its weight of zinc. In Germany and Sweden, the proportion of zinc varies from one-fifth to one-fourth of the copper. Twenty to forty parts of zinc, with eighty to sixty parts of copper form the _cuivre jaune_, laiton, or yellow copper of the French. Dutch metal, or Dutch gold, is a fine kind of brass, and comes in leaf, which is about five times as thick as gold leaf. This brass is made by the cementation of copper plates with calamine, and hammered out into leaves. According to Thenard (_Traité de Chimie_, tome i, p. 478), the French use 50 parts of calamine, mixed intimately with 20 parts of charcoal, and stratified in a crucible with 30 parts of laminated, or granulated copper. British brass consists of two parts of copper, and 1-1/8 parts of zinc, by weight. The filings of brass are much employed in fire-works. They communicate to stars, rains, &c. a flame between a blue and green. In some, the filings of copper alone are used. A beautiful green fire, for instance, is produced by 16 ounces of gunpowder, and 3-1/4 ounces of copper-filings. Verdigris is also employed for the same purpose; but the effect is not so striking, as in that preparation, the copper is already oxidized. The effect of copper in fire-works, it is to be recollected, depends, like that of other metals, on its combustion, and consequent oxidizement. The product of the combustion of brass, is oxide of copper, and oxide of zinc. _Sec. XLIV. Of Bronze._ The union of copper with tin, in various proportions, forms gun-metal, bell-metal, the mirrors of telescopes, and bronze. The ductility of the copper is diminished by the tin; but its hardness, and tenacity, as well as its fusibility and sonorousness are increased. To form a complete union of the two metals, they should be continued in fusion for some time, and constantly stirred. The tin is apt to rise to the surface, unless this precaution is used. Bronze is usually composed of 100 parts of copper, and 8 to 12 parts of tin. It is yellow, brittle, heavier than copper, and has more tenacity.