The silver alloys with aluminum bronze, as represented in the four following atomic formulas, are of a rich gold color, and well adapted for jewelry, watch cases, etc.: Cu Al Ag Ag + 24 (Al + Cu_{6}) = 0.9180 + 0.0616 + 0.0203 Ag + 24 (Al + Cu_{7}) = 0.9241 + 0.0570 + 0.0188 Ag + 24 (Al + Cu_{8}) = 0.9330 + 0.0504 + 0.0166 Ag + 24 (Al + Cu_{9}) = 0.9400 + 0.0450 + 0.0150 The figures being proportional weights. A cheap alloy for journal boxes and machinery may be made by substituting zinc for silver in the following atomic proportions: Cu Al Zn Zn + 2(Al + Cu_{6}) = 0.8643 + 0.0622 + 0.0734 Zn + 2(Al + Cu_{9}) = 0.9053 + 0.0435 + 0.0512 Zn + 2(Al + Cu_{12}) = 0.9273 + 0.0333 + 0.0394 This is subject to considerable shrinkage in casting, but is tenacious, and when drawn into wire has a tensile strength of ninety to one hundred thousand pounds. The following alloys, in which iron enters as a third element, are well adapted for gun metal, being hard, tenacious, laminable, and ductile: Cu Al Fe Fe + (Al + Cu_{15}) = 0.9203 + 0.0267 + 0.0530 Fe + (Al + Cu_{9}) = 0.9399 + 0.0446 + 0.0149 Also a four-element alloy of Cu Al Zn Fe 1. Fe + Zn + (Al + Cu_{12}) = 0.8386 + 0.0305 + 0.0712 + 0.0600 2. Fe + Zn + (Al + Cu_{15}) = 0.8666 + 0.0249 + 0.0588 + 0.0496 The tensile strength of the above alloys as drawn wire is 82,000 pounds for the first, and 107,000 pounds for the second. All of the alloys in which zinc or zinc and iron enter in place of silver, the color is affected and the luster diminished. With nickel and platinum for the third element, we have: Cu Al Ni Ni + 6 (Al + Cu_{6}) = 0.9129 + 0.0634 + 0.0237 Pl + 21 (Al + Cu_{6}) = 0.9117 + 0.0656 + 0.0225 Those alloys into which platinum is introduced are less affected by acids than those in which silver takes the place of platinum; platinum producing a higher luster than silver. In the alloys of aluminum bronze with the more difficultly fusible metals, it is preferable to fuse the bronze first, then add the other metal in small shavings or wire; by this means the less fusible metal absorbs the other without raising the heat of the furnace excessively. Add the least fusible metal last, a little at a time, allowing the heat of the melted metal to fall by degrees, which prevents boiling and evaporation. The crucibles for mixing the alloys should be of plumbago lined with a paste of lime. Avoid sand crucibles, as silicium may be reduced and absorbed by the aluminum, inducing brittleness. If found brittle, remelt with cryolite as a flux, or stir the melted metal or alloy with a hard wood stick that has been slightly charred.