Page:Popular Science Monthly Volume 27.djvu/555

Rh, phosphor-manganese bronze, phosphor-lead bronze, phosphor-tin, aluminum-bronze, silveroid, and cobalt-bronze. There are also other bronzes which are used as substitutes for gold in cheap imitation jewelry, but they do not come within the scope of the present paper.

The action of phosphorus on copper alloys is principally due to its reducing qualities, by virtue of which the oxygen absorbed by the molten metal is removed, or the oxides formed thereby are eliminated, and the degree is imparted of homogeneity, strength, and toughness peculiar to the chemically pure metal. The phosphorus, by producing these effects, is converted into a cuprous oxide, which floats on the surface of the molten metal in the shape of a very fluid slag, while the superfluous quantity combines with the metal. It is not, therefore, desirable to add to the bronze a larger quantity of phosphorus than will suffice to reduce the oxide present.

Phosphor-bronze was first prepared by Dr. Kunzel, of Dresden, and was brought into practical use in England early in 1873. The alloys of this class are composed of copper, tin, and phosphorus, and other ingredients in variable proportions, and are made to be either as ductile as copper, as tough as iron, or as hard as steel, according as the proportions of the constituents are varied. The alloys used for rolling and drawing have very different proportions from those employed for castings, bearings, and parts of machinery. The castings of this metal are perfectly sound and homogeneous. Wherever strength, toughness, and durability are desired, phosphor-bronze is found to be better adapted than gun-metal and brass, and in many cases than iron and steel. Having the advantage of not becoming crystalline under the action of repeated shocks and bendings, it is well adapted for making wire-rope, and, not being acted upon by corrosive liquids or the atmosphere, its value as a metal remains constant. The principal varieties of phosphor-bronze, which are produced by slightly varying the proportions of the constituents, are phosphor-bronze duro A, a very dense metal, adapted for bearings carrying heavy wheels running at great velocities, and generally for all quick-speed purposes; and phosphor-bronze duro B, which is intended for the bearings of hot-neck rolls, and for all bearings having to withstand great pressure.

Silicium-bronze was invented by M. Lazare Weiller, of Angoulême, in the search for a material for telegraph-wires, which, together with all the desirable properties of phosphor-bronze, should have a better conducting power. In it phosphorus is replaced by a silicious metalloid, by the incorporation of which a wire is produced offering the same resistance to rupture as phosphor-bronze wire, by the use of which telegraph lines may be furnished with a light, unoxidizable wire, having all needed electrical efficiency. It is also affirmed of wires of this bronze that they are of equal strength with ordinary wires, while not one tenth as heavy; and that, if broken, they will not fall to the