468 



BRASS 



e e e, vents in the roof of the hot chamber /; g, g, two plates for shutting the hot 

 chamber ; h, the flue ; i, the chimney. After rolling, the sheets, covered with black 

 oxide of copper, are plunged for a few minutes into a mother-water from the alum 



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works, then washed in clean water, and lastly, smeared with oil, and scraped with a 

 blunt knife. 



For musical purposes, the brass wire of Berlin had acquired great and merited 

 celebrity ; but that of Birmingham and of Cheadle is now preferred by foreigners. 



The Table on the opposite page, for the compilation of which wo are indebted to 

 Mr. Robert Mallet, F.R.S., presents, in a very intelligible form, the chemical and 

 physical conditions of the various kinds of brass. 



It is known that common brass, containing from 27'4 to 31 '8 per cent, of zinc and 

 from 71'9 to 65'8 per cent, of copper, is not malleable while hot, but that articles of 

 it must be made by casting. As it would be of great advantage in many branches of 

 industry to have an alloy of this kind that could be worked while hot, like malleable 

 iron, the information that such an alloy exists must be welcome to artists. 



By melting together 33 parts of copper and 25 parts of zinc, there was a loss of 3 

 parts, thus making 60 per cent, copper and 40 per cent. zinc. It differs from the 

 English specimens by containing a larger proportion of zinc, and possesses, according 

 to M. Machts, the proprietor of a brass foundry in Hanover, the precious property of 

 malleability in a higher degree than the English specimens. 



A piece of ' yellow metal,' similar in colour to this alloy, was found on analysis to 

 contain 60*16 copper and 39'71 zinc, which is the composition of malleable brass. It 

 also showed groat density or solidity. 



An alloy was prepared by melting together 60 parts copper and 40 parts zinc, which 

 had the following properties : The colour was between that of brass and tombak, it 

 had a strong metallic lustre, a fine close-grained fracture, and great solidity (density). 

 Its specific gravity at the temperature of 10 C. was 8'44 ; by calculation it ought 

 only to have been 8 '08 ; thus showing that in the formation of the alloy a condensa- 

 tion must have taken place. Calculation shows that the alloy may be considered as 

 a determinate chemical combination, for the results of the analysis very nearly accord 

 with the assumption that it may be considered as composed of three atoms by weight 

 of copper and 2 atoms by weight of zinc (3Cu + 2Zn). The hardness of the alloy 

 is the same as that'of fluor spar ; it can be scratched by apatite (phosphate of lime), 

 consequently its hardness is = 4. The alloy is harder than copper, very tough, and 

 is, in a properly managed fire, malleable; so much so that a key was forged out of a 

 cast rod. 



These important properties of this alloy warrant an expectation of its application 

 to many purposes in the arts, and it would appear that they depend on its definite 

 chemical proportions. 



We learn some further particulars from the ' Gewerbeverein,' of Lower Austria. 

 The commission obtained from an English specimen 65'03 of copper and 34'76 zinc. 



