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Aluminum Bronze

The best quality of aluminum bronze is made by alloying copper with from five to ten per cent of aluminum.

The alloy is far superior to any of the common bronzes, being far more rigid--chips, files, and machines better; the turnings not being short and chippy, like brass or cast-iron, but long and connected after the manner of the best mild steel. It has a beautiful gold color, takes a splendid polish, does not easily tarnish, works well under the artist's tools; and, while it makes an excellent imitation gold, and as such is used extensively for a great variety of objects, useful and ornamental, yet it is unquestionably the king of alloys for guns, journal-bearings, bells, and many other purposes too numerous to enumerate here, owing to its great tenacity, malleability, and good wearing qualities, the fineness of its grain making it a highly desirable alloy for all parts of machinery that are subjected to friction. Like copper, its qualities of softness and ductility are improved by sudden cooling, and, strange to say, like iron, it may be forged and welded--something utterly impossible with other alloys. But to obtain the best results it is absolutely necessary that the best copper and the purest aluminum be used for making the alloy. See ALUMINUM; ALUMINUM ALLOYS. Amalgam means that class of alloys with which mercury forms one of the combining metals. With regard to the nature of the union that takes place in such combinations it has been remarked that, on adding successive small quantities of silver to mercury, a variety of fluid amalgams are apparently produced. Really, the chief, if not the only, compound resulting from this operation is a solid amalgam, which is intimately diffused throughout the fluid mass. In other words, the fluidity of an amalgam depends on there being an excess of mercury over and above the amount required to form a definite compound. Mercury immediately combines with silver and gold at common temperatures, but with iron, even when hot, it is not disposed to unite. See AMALGAMATION; MERCURY.

Amalgamation is the operation of mixing mercury with any metal to form an amalgam. This is done by fusing the metal first and adding the mercury to it, on which they at once mutually attract each other. The amalgam of gold with mercury is made by beating gold (1 drachm) into thin plates and setting them into a red-hot crucible; the mercury (1 ounce) is then poured in, and the whole well stirred with an iron rod until it begins to fume, when it must be poured into water to coagulate. Some processes of gilding and silvering are conducted by amalgamation (see MERCURY); but its most extensive use is in separating metals, silver especially, from their ores by dissolving the particles of metal and leaving the earthy matter. Substantially, the process consists of first crushing the quartz rock, in which the particles of gold are imbedded, by means of stamp-mills, and placing the dust, mixed with mercury, into rapidly revolving vessels. The mercury, by this process, attaches to itself all the gold particles and forms a semi-fluid mass, which is mercury in a half-congealed state, containing all the gold. This amalgam is then placed in a retort and heat applied; which operation separates the mercury by sublimation, to be again employed for further amalgamation, and leaves the collected gold in the body of the retort. See AMALGAM; SUBLIMATION; MERCURY; SILVER; GOLD.