. A dictionary of arts, manufactures and mines : containing a clear exposition of their principles and practice. COPPER. 333 consumption of pit-coal amounts to 36 cwt. As soon as the copper is melted, thebellows are set a-going, and the surface of the metal gets soon covered with a 308. moderately thick layer of cinder, which is drawn off. This is the first skimming ordecrassage. By and by, a second layer of cinder forms, which is in like mannerremoved; and this skimming is repeated, to allow the blast to act upon fresh metallicsurfaces. After 4 or 5 hours, no more slag appears, and then the f
. A dictionary of arts, manufactures and mines : containing a clear exposition of their principles and practice. COPPER. 333 consumption of pit-coal amounts to 36 cwt. As soon as the copper is melted, thebellows are set a-going, and the surface of the metal gets soon covered with a 308. moderately thick layer of cinder, which is drawn off. This is the first skimming ordecrassage. By and by, a second layer of cinder forms, which is in like mannerremoved; and this skimming is repeated, to allow the blast to act upon fresh metallicsurfaces. After 4 or 5 hours, no more slag appears, and then the fire is melted mass now begins to boil or work (travailler), and continues so to do, forabout I of an hour, or an hour, after which the motion ceases, though the fire be keptup. The gahrproof is now taken; but the metal is seldom fine in less than | of anhour after the boil is over. Whenever the metal is run off by the tap-hole into thetwo basins i i, called split-hearths, a reddish vapor or mist rises from its surface,composed of an infinite number of minute globules, which revolve with astonishingvelocity upon their axes, constituting what the Germans called spratzen (crackling) ofthe copper. They are composed of a nucleus of metal, covered with a film of protoxyd
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Keywords: ., bookcentury1800, bookdecade1840, booksubje, booksubjecttechnology
