The Penn's Grove record., 1884-07-19
Brass.

of gold; it is more fusible than copper,
less subject to rust and to be acted upon
by the vast variety of substances which
corrode copper with so much case; and
1t is equally malleable when cold, and
more eXtensible than either copper or
iron, and hence Is well fitted for fine
wire. Brass, however, is only MALE
able when cold. Hammering Is found
to give a magnetic quality to brass, and
this circumstance makesi 1t necessary to
employ unhammered brass for compass
boxes and similar apparatus.
The expansion of brass has been very
accurately determined, as this metal is
most commonly used for mathematical
and astronomical instruments, where
the utmost precision is required. Mr..
Smeaton found that II inch n length
of cast brass, at 32o, expand by 1902
Of heat Tor the interval fromi ling to
boiling water) oops part of an inch
Brass wire under the same clrcum-
stances expanded 232 parts; an alloy of
16 of brass with one l Of tin expanded
300 parts. The expansion of hammered
copper is only 204 such parts, but that
Of zinc is 253, so that brass holds a
middle place in this respect between its
two component metals.
Most of the zinc readily burns off
from brass when kept melted in a strong
heat with free access of air. When the
heat is g lal to that of melted copper,
the zIni takes fire and slowly burns
away. AT last little else but copper re-
mainf but still united with a small por-
ton I zinc, which no further continu-
nee of the fire will entirely separate.
Some kinds of very fine brass are said
not to be made by concentration, but by
a more speedy and direct union of cop
per and zinc, care being taken to pre-
vent the access Of air to the materials
while in fusion. Very fine brass may
also be made by mixing together the
oxides Of copper and zinc and reducing
them with a carbonaceous fux. Sage
gives the following experiment to this
purpose: Mix together so grains Of the
oxide OF copper, remaining after the
dlstillation of verdigris (which is very
pure), with 100 grains Of lapis calamin-
aris, 400 grains of black flux, and 30
grains of charcoal powder; melt the
mixture in a crucible till the blue flame
is seen no longer round the I'D of the
crucihle, and when cold a fine button
of brass is found beneath the scoria,
weighing a sixth more than the copper
alone, obtainable from its oxide in the
same way, but without the calamine.
This brass has a very fine color, Ike
gold.
On this experiment N. Sage observes
that there appears to be a point Of NUT
ual s~aturation between the two metals,
which is when the copper retains one
sixth of zinc, and this portion it will
retain however long it is heated, pro-
vided the surface of the melted metal
be covered to protect the zinc from the
action of the air; but if the brass con
tains a greater proportion of zinc, pre-
cisely this excess will escape, ven in
covered vessels, and will burn when 1t
comes out to the AIR.
The same chemist also observes that
the color Is the finest at the above pro.
portion. These experiments seem to
require further confirmation, but we
may reckon that to be the most perfect
brass which is composed of about 1928
per cent. of zinc and So. Y of copper,
and which is not liable to any alteration
in its constituent parts by successive
or long continued fusions, provided the
access of air be prevented.
Analysis shows a vast variety in the
proportions of the different species of
brass used in commerce. In general
the extremes of the highest and lowest
proportions of zinc are from II to 20
per cent. of the brass. Even with so
much as 25 per cent. of zinc, brass, if
well manufactured, is perfectly malle-
able, though zinc itself scarcely yields
to the hammer. NJ. Die analysed a
specimen Of remarkably fine brass made
at Geneva, for the purpose Of escape
ment wheels and the nicer parts Of
matchmaking, the perfect bars of which
bear a very high price. This metal
unites a great beauty of color to a very
superior degree Of ductility. 1t was
found to consist Of 70 Of copper with 25
Of zinc, and, probably, too, the copper
was Swedish, or some other of the finer
sorts. The common brass Of Paris
seems to contain about IL per cent. Of
zinc, the English probably more,
Brass is applicable to an infinite va
riety of purposes, is easily wrought by
casting and hammering, and by the
lathe, its wire is emlnently useful, and
it takes a high and very beautiful pol
ish. The appearance of brass Is given
TO other metals, by washing them with
a yellow lacquer or yarnish, a substitu-
tion often very much to the detriment
oft he manufactured article.