BRASS (O. Eng. braes) , an alloy consisting mainly if not exclusively ofcopper and
See also:zinc; in its older use the
See also:term was applied rather to alloys of copper and tin, now known as
See also:bronze (q.v.) . Thus the brass of the 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 Romans comprehended a brass compound of copper and zinc under the term orichalcum or aurichalcum, into which Pliny states that copper was converted by the aid of cadmia (a
See also:mineral of zinc) . In England there is
See also:good evidence of the manufacture of brass with zinc at the end of the 16th century, for
See also:Elizabeth by patent granted to
See also:William Humfrey and 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 City of
See also:London of and for the Mineral and 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 series of metals is obtained which simulate gold more or less closely; such are Dutch
See also:Mannheim gold, similar and pinchbeck, the last deriving its name from a London clockmaker, Christopher Pinchbeck, who invented it in 1732 . 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: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 ofiron, a fact of which
See also:advantage is taken in the production of Aich's metal and
See also:delta metal . Of the latter there are several varieties, modified in composition to suit different purposes . Some of them possess high tensile strength and ductility . They are remarkably resistant to corrosion by
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: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: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: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 air; the brilliancy of the
See also:surface can, however, be preserved if the metal is thoroughly cleansed by " dipping " in nitric acid and " lacquered " with a coating of
See also:varnish consisting of seed-
See also:lac dissolved in spirit .
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