ON THE HARDNESS OF METALS AND ALLOYS. 117 
attention of engineers. There is in this series an alloy to 
which we wish to draw special attention, viz., the alloy 
Cu Zn composed in 100 parts of 
Wonper? yilis 228s .ds 49°32 
PUB O ye «Bia. EGRET. Ses 50°68 
100:00 
Although this alloy contains about 20 per cent. more 
zinc than any of the brasses of commerce, still it is, when 
carefully prepared, far richer in colour than the ordinary 
alloys of commerce. The only reason that we can give 
why it has not been introduced into the market is, that 
when the amount of zinc employed exceeds 33 per cent. the 
brass produced becomes so white that the manufacturers 
have deemed it advisable not to exceed that proportion. 
If, however, they had increased the quantity to exactly 
50°68 per cent. and mixed the metals well, they would 
have obtained an alloy as rich in colour as if it had con- 
tained 90 per cent. of copper, and of a hardness three 
times as great as that given by calculation. In order 
to enable engineers to form an opinion as to the value of 
this cheap alloy we give them the degrees of hardness of 
several commercial brasses : — 
Tl 
Commercial Brasses, Weight Cast Iron = 1000. 
employed, | Obtained. | Calculated. 
lbs. 
Copper 82°05 
*Targe Bearing” ......... {sti 12°82 
Zinc 513 | 2700 562 259 
Copper 80 
“GI Se js 10 
Zine 10 3600 750 262 
“y, ” Copper 64 
Yellow Brass” .,........-. { Fae 36 2500 520 258 
Copper 80:0 
*Ti : 
“Pumps and Pipes” ...... Sa oe 
Lead 75 | 1650 343 257 
eC TE EL LTE EE TD 
* These alloys all contain tin. 
