Lead

a soft, bluish gray metal with high lustre. Lead is 11.37 times as heavy as water. It melts at 619 deg. F. If melted in the air, the surface becomes coated with dross, giving an impression of impurity, but it is simply a combination of lead and oxygen. By removing the crust and allowing air access to the pure molten lead a new coating will form and so on until the lead is used up. Lead, in quantity, is almost as poisonous as mercury. Absolutely pure water, which, by the way, is tasteless and without sparkle, dissolves a small amount of lead in open air, but ordinary water does not. The Latin name of lead is plumbum; whence the terms plumbing, plumber, and plumb-line.

Lead occurs in nature in several minerals, the most important of which is a compound of lead and sulphur, known as galena. Galena, Illinois, takes its name from this ore. In the United States, lead ore has been found in the mountains from Maine to Georgia, but not in very profitable quantities. The Missouri lead district includes the lead ores of Kansas, Wisconsin, Illinois, and adjacent states. It centers commercially in St. Louis and has given that city an importance of long standing as a producer of ammunition. The first mining of Colorado was that of lead at Leadville on the head waters of the Arkansas River where a most remarkable silver-lead lode was discovered. Utah has important lead-silver mines. The famous Coeur d'Alene mine of Idaho yields as high as 60,000,000 pounds of lead a year. Montana and Arizona, in short all the mountainous states of the West, produce lead. Until of late, Spain has led the world in the production of this metal. The following table gives the world production in tons for 1907:

Total, tons . . . . . 972,160

Lead is combined with carbon to produce the white lead used in paints. This is its most extensive use. Next in importance is the use in lead pipe and sheet lead employed by plumbers. There is just a chance of water, tinged with certain acids, dissolving enough lead to be poisonous; but the danger is so slight, and lead is so free from rust and bends into crannies so easily, that it is a favorite metal. Large quantities of lead are used in making shot. The lead is mixed with a little arsenic, three parts out of 700, to make it harder and to cause it to assume a more perfectly spherical form when dropped through the air. Manufacturers erect tall shot towers, as at St. Louis. The molten lead is poured through a sieve at the top of the tower and has time in falling not only to gather in globules, but to harden ere it falls into a tank of water at the foot. The shot is then run over sieves to assort it into sizes.

Type is made from lead and antimony combined in the ratio of seventy-six parts of lead to twenty-four of antimony. The antimony is added to give hardness and also because it expands slightly in cooling and gives a clear-cut, sharp face to the type. The pigment known as chrome yellow is chromate of lead. Lead was one of the metals known to the ancients, who called it saturn. Lead poisoning was known as saturnine poisoning.

See Plumbing; Graphite; Paint; Type