Lead is seldom found in a pure state, but usually as the carbonate (PbC03), the sulphate (PbS04), or the sulphide galena (PbS). To obtain lead it is necessary to free the ore of its combining elements. The processes of stamping, washing, and smelting are used for this purpose.
The ore put into the furnace should consist of from five to eight different kinds, as a mixture of ores produces better lead. This charge is first roasted to oxidize the sulphur or arsenic contained in the ore to sulphur dioxide and arsenic oxide. After the remaining ore has been fused, a layer of slag or refuse forms to the depth of two or three inches. The slag is drawn off, and then the molten lead is allowed to run into a pan where it is skimmed and ladled into molds.
Lead sheets are used by the plumber for roofing, for making pipes, cisterns, tanks, leaden coffins, and for many other purposes. The ease with which lead can be worked causes it to be employed in all countries which have arrived at any degree of civilization. The Chinese use large quantities for making the thin sheets in which they pack their tea. Their process for making these sheets is simple and ingenious. One workman sits on the floor with one large flat stone before him and another at his side. A second workman stands by with a pot of melted lead, part of which he pours on the stone. The first workman places the movable stone on the melted metal and compresses it into a flat thin sheet which is afterwards trimmed. The process is expeditious and effectual.