. A dictionary of arts, manufactures and mines : containing a clear exposition of their principles and practice. s passed by increase of temperature from the pasty into the liquid state. Coolingbrings back the sludge to the pasty condition, and is therefore necessary for the dueseparation of the different bodies. The drying up of the thin slags by lime is intendedto liberate the oxyde of lead, and allow it to react upon any sulphuret which may have 762 LEAD. resisted roasting or decomposition. It is also useful as a thickener, in a mechanical pointof view. The iron of the tools, which wear awa
. A dictionary of arts, manufactures and mines : containing a clear exposition of their principles and practice. s passed by increase of temperature from the pasty into the liquid state. Coolingbrings back the sludge to the pasty condition, and is therefore necessary for the dueseparation of the different bodies. The drying up of the thin slags by lime is intendedto liberate the oxyde of lead, and allow it to react upon any sulphuret which may have 762 LEAD. resisted roasting or decomposition. It is also useful as a thickener, in a mechanical pointof view. The iron of the tools, which wear away very fast, is also serviceable in re-ducing the sulphuret of lead. The small coal added along with the lime at Grassington,and also sometimes at Holywell, aids in reducing the oxyde of lead, and in transformingthe sulphate into sulphuret. 3. The smelting furnace or ore hearth.—This furnace, called by the French ecossais, isfrom 22 to 24 inches in height and 1 foot by 1| in area inside ; but its horizontal section,always rectangular, varies much in its dimensions at difierent levels, as shown infiS- The hearth and the sides are of cast iron; the sole-plate a b is also of cast iron, 2^ inchesthick, having on its back and two sides an upright ledge, a c, 2^ inches thick and 4|high. In front of the hearth there is another cast iron plate m n, called the uorhstone, surrounded on every side excepting towards the sole of the furnace, by a ledgeone inch in thickness and height. The plate slopes from behind forwards, and its pos-terior ledge, which is about 4| inches above the surface of the hearth, is separated fromit by a void space q, which is filled with a mixture of bone ash and galena, both in finepowder, moistened and pressed down together. The melted lead cannot penetrate intothis body, but after filling the basin at the bottom of the furnace, flows naturally outby the gutter (nearly an inch deep) through a groove in the work-stone; and thenpasses into a caldron of rec
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Keywords: ., bookcentury1800, bookdecade1840, booksubje, booksubjecttechnology
