470 BRASS 



Eisner analysed a malleable brass, and found it to contain 61-16 copper and 3971 

 zinc. Those numbers approximate to the composition Cu'Zn 3 (69'4 per cent, copper 

 and 40'6 zinc). Liebig and Kopp's Report. 



The alloy noticed in the preceding paragraphs is identical with that known as 

 1 Muntz's patent sheathing ' (see table on preceding page). 



The chief properties of value in brass, are its colour, hardness (which is superior 

 to that of copper), and power of taking delicate impressions when cast in a mould. 



The malleability of brass varies greatly with its chemical composition, and with 

 the temperature at which it is worked. As a rule, the malleability diminishes with 

 the increase in the quantity of zinc. 



The effect of the admixture of foreign metals on brass is somewhat similar to that 

 produced by them in copper. Antimony is most injurious, as it renders the metal 

 brittle and liable to crack at the edges in rolling. 



Lead also has a hardening effect on brass, and is useful for all work that requires 

 to be turned or filed ; as the addition of about two per cent, causes the turnings to 

 break short, and thus prevents the tool from becoming clogged. The same effect is 

 produced in brass for engraving by the addition of a small quantity of tin. 



Brass is apt to undergo a gradual molecular change, especially if subjected to vibra- 

 tion, and thus becomes extremely brittle. Hence, it happens that brass chains used 

 for suspending heavy objects, like chandeliers, occasionally snap without any external 

 violence. 



Thin sheet brass may be readily stamped into shape, and in this way ornamental 

 brass objects are now extensively made : the sheet brass being subjected to heavy 

 blows delivered by steel dies. The metal requires, however, to be frequently an- 

 nealed during the stamping, and the film of oxide which is formed on the surface by 

 the annealing, requires to be removed by dipping in aquafortis ; the objects are then 

 washed with water, and lacquered. By varying the strength of the aquafortis, the 

 colour of the brass may be considerably modified. 



The surface of brass work requires to be protected from the action of the air, by a 

 coating of a less oxidisable metal, or a resinous varnish or lacquer. The metal is 

 first brought up to a clean face by the process of ' dipping ' or immersion into weak 

 nitric acid, whereby the adherent scale or oxide formed during annealing is removed. 

 By varying the strength of the acid employed, and repeating the dipping, the metal 

 may be made to assume a ' matt,' dead, or frosted appearance. After dipping, the 

 metal is washed in water, and dried by imbedding it in hot sawdust. The lacquer, 

 which is an alcoholic solution of shellac, more or less coloured with dragon's blood, 

 according to the tint desired in the finished work, is brushed over the article when 

 in a heated state, and dried over a stove. The colour in the lacquer helps to produce 

 a higher or more golden tint than that due to the metal alone. 



Brass work is bronzed in several different ways : the most usual are, immersion in 

 a solution of arsenious acid, in hydrochloric acid, or in bichloride of platinum. The 

 former is chiefly employed for cheap work, such as common gas fittings, while the 

 latter is used for blacking or bronzing telescopes, mathematical instruments, and 

 similar fine work. The effect, in either case, is the production of a film of dark 

 coloured metal on the surface of the brass, namely, arsenic in the former, and 

 platinum in the latter case. This operation is performed after dipping, and before 

 lacquering. 



Another method now extensively used, is to apply a coating of a solution of cor- 

 rosive sublimate (bichloride of mercury) in water, mixed with vinegar. A film of 

 mercury is thus formed on the surface of the brass. 



For the method of covering brass with a film of tin, see PIN MANUFACTURE. 



BRASS Foil. Dutch leaf, called Knitter or Rauschgold in Germany, is made from 

 a very thin sheet brass, beat out under a hammer worked by water-power, which gives 

 from 300 to 400 strokes per minute, from 40 to 80 leaves being laid over each other. 

 By this treatment it may be reduced to loaves not more than S0 ^ u6 th of an inch thick. 

 The metal employed is one rich in copper. 



BRASS, YELLOW. The following Table exhibits the composition of several varieties 

 of this species of brass. No. 1 is a cast brass of uncertain origin ; 2, tho brass of 

 Jemappes ; 3, the sheet brass of Stolberg, near Aix-la-Chapello ; 4 and 5, the brass 

 for gilding, according to D'Arcet ; 6, the sheet brass of Ilomilly ; 7, English brass 

 wire ; 8, Augsberg brass wire ; 9, Brass wire of Neustadt-Eberswald, in the neigh- 

 boxirhood of Berlin : 



