USES OF LEAD
Lead is used in the form of the metal, of alloys with other metals, and of various chemical compounds. As metal its chief uses are as pipe for water and corrosive solutions; for protective covering of electrical cables; as sheet lead for lining chambers for the manufacture of sulphuric acid and vats for chemical manufacturing processes. In smelting, lead is used as a collector of other metals, particularly of gold and silver, from which it is later separated, now most generally by the use of zinc by the Parkes process of desilverization.
Lead alloys readily with nearly all other metals in all proportions. Its alloys of industrial importance comprise type metal, bearing or babbitt metals, shot, solders, casting metals, some brasses, and the fusible alloys used for the protection of electrical apparatus and in automatic sprinklers for the protection of buildings against fire. Type metal, originally composed of 83 per cent. lead and 17 per cent. antimony, now often contains bismuth and sometimes a little copper and iron. An alloy of 9 parts lead, 2 antimony and 2 bismuth is used for stereotype plates. Less than 2 per cent. of arsenic is added to lead used to make shot to increase the hardness and sphericity of the product. Antimony also imparts the hardness essential to shrapnel, etc. Bearing metals comprise alloys of lead and antimony or these with copper, tin, and zinc. Antimony imparts to lead the property of expansion on solidification, essential to type metal and casting materials generally. Lead makes a brass that is soft and machines easily. Solder is commonly an alloy of lead and tin. The melting point varies with the proportions of these constituents and others, sometimes added for special purposes. The cheapest solder in general use is 30 per cent. tin and 70 per cent. lead. Solders seldom contain more than 50 per cent. tin. The addition of bismuth, cadmium, or mercury lowers the melting below the boiling point of water. Fuses can thus be obtained which interrupt electric circuits at any desired temperature.
The largest uses of lead compounds are as pigments. White lead or basic carbonate, 2(PbCO3)Pb(OH)2, is the most extensively consumed, being used alone or mixed with zinc oxide and barytes. Red lead (Pb3O4) is used for painting structural steel, as a pipe-joint cement, and in the manufacture of glass. Litharge, another oxide, is used in assaying as a flux, in rubber manufacture, and in making glass. The acetate, carbonate and other chemical compounds are used in medicine.
The relative amounts of lead consumed in the various uses in 1913 were: In pigment, comprising white lead, red lead, litharge, and orange mineral, 38.0 per cent.; in alloys such as type metal, bearing metals, and solders, 29.7 per cent.; in pipe, 15.2 per cent.; in shot, 10.4 per cent.; and in sheets, 6.7 per cent.