In general brass is composed of two-thirds copper and one-third zinc, but a little lead or tin is sometimes advantageous, as the following:

I

Red copper, 66 parts; zinc, 34 parts; lead, 1 part.

II

Copper, 66 parts; zinc, 32 parts; tin, 1 part; lead, 1 part.

III

Copper, 64.5 parts; zinc, 33.5 parts; lead, 1.5 parts; tin, 0.5 part.

Brass-Aluminum

A small addition of aluminum to brass (1.5 to 8 per cent) great-

ly increases its hardness and elasticity, and this alloy is also easily worked for any purpose. Brass containing 8 per cent of aluminum has the valuable property of being but slightly affected by acids or gases. A larger percentage of aluminum makes the brass brittle. It is to be noted that aluminum brass decreases very materially in volume in casting, and the casts must be cooled slowly or they will be brittle. It is an alloy easily made, and its low price, combined with its excellent qualities, would seem to make it in many cases an advantageous substitute for the expensive phosphorous bronze.

Bristol Brass (Prince's Metal)

This alloy, which possesses properties similar to those of French brass, is prepared in the following proportions:

I         II III

Copper............ 75.7 67.2 60.8

Zinc............... 24.3 32.8 39.2

Particular care is required to prevent the zinc from evaporating during the fusing, and for this purpose it is customary to put only half of it into the first melting, and to add the remainder when the first mass is liquefied.