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BRASS (O. Eng. braes)

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Originally appearing in Volume V04, Page 434 of the 1911 Encyclopedia Britannica.
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BRASS (O. Eng. braes) , an alloy consisting mainly if not exclusively of See also:copper and See also:zinc; in its older use the See also:term was applied rather to See also:alloys of copper and See also:tin, now known as See also:bronze (q.v.). Thus the brass of the See also:Bible was probably bronze, and so also was much of the brass of later times, until the distinction between zinc and tin became clearly recognized. The Latin word aes signifies either pure copper or bronze, not brass, but the See also:Romans comprehended a brass See also:compound of copper and zinc under the term orichalcum or aurichalcum, into which See also:Pliny states that copper was converted by the aid of cadmia (a See also:mineral of zinc). In See also:England there is See also:good See also:evidence of the manufacture of brass with zinc at the end of the 16th See also:century, for See also:Queen See also:Elizabeth by patent granted to See also:William Humfrey and See also:Christopher Schutz the exclusive right of working See also:calamine and making brass. This right subsequently devolved upon a See also:body called the " See also:Governors, Assistants and See also:Societies of the See also:City of See also:London of and for the Mineral and See also:Battery See also:Works," which continued to exercise its functions down to the See also:year 1710. When a small percentage of zinc is See also:present, the See also:colour of brass is reddish, as in tombac or red brass, which contains about ro %. With about 20% the colour becomes more yellow, and a See also:series of metals is obtained which simulate See also:gold more or less closely; such are Dutch See also:metal, See also:Mannheim gold, similar and pinchbeck, the last deriving its name from a London clockmaker, Christopher Pinchbeck, who invented it in 1732. See also:Ordinary brass contains about 30 % of zinc, and when 4o % is present, as in Muntz, yellow or patent metal (invented by G. F. Muntz in 1832), the colour becomes a full yellow. When the proportion of zinc is largely increased the colour becomes See also:silver-See also:white and finally See also:grey.

The limit of See also:

elasticity increases with the percentage of zinc, as also does the amount of See also:elongation before fracture, the maximum occurring with 30 %. The tenacity increases with the proportion of zinc up to a maximum with 45 %; then it decreases rapidly, and with 5o °/, the metals are fragile. By varying the proportion between 30 and 43 % a series of alloys may be pre-pared presenting very varied properties. The most malleable of the series has an elongation of about 6o %, with a tensile strength of 17.5 tons per sq. in. Increase in the proportion of zinc gives higher tensile strength, accompanied, however, by a smaller percentage of elongation and a materially increased tendency to produce unsound castings. The quality of copper-zinc alloys is improved by the addition of a small quantity of See also:iron, a fact of which See also:advantage is taken in the See also:production of Aich's metal and See also:delta metal. Of the latter there are several varieties, modified in See also:composition to suit different purposes. Some of them possess high tensile strength and ductility. They are remarkably resistant to corrosion by See also:sea-See also:water, and are well suited for See also:screw-propellers as well as for See also:pump-plungers, pistons and glands. Heated to a dull red delta metal becomes malleable and can be worked under the See also:hammer, See also:press or stamps. By such treatment an ultimate tensile strength of 3o tons per sq. in. may be obtained, with an elongation of 32 % in 2 in. and a See also:con-See also:traction of See also:area of 30 %. In the arts brass is a most important and widely used alloy.

As compared with copper its See also:

superior hardness makes it See also:wear better, while being more fusible it can be See also:cast with greater facility. It is readily See also:drawn into See also:fine See also:wire, and formed into rolled sheets and rods which are machined into a huge number of useful and ornamental articles. It is susceptible of a fine See also:polish, but tarnishes with exposure to the See also:air; the brilliancy of the See also:surface can, however, be preserved if the metal is thoroughly cleansed by " dipping " in nitric See also:acid and " lacquered " with a coating of See also:varnish consisting of See also:seed-See also:lac dissolved in spirit.

End of Article: BRASS (O. Eng. braes)

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