COPPER ASSAYING 



941 



3. Reduction or Fusion for coarse-copper ; the oxide of copper being reduced to metal, 

 and the oxide of iron retained in the slag. 



4. Refining of the coarse-copper. 



All the ores of copper, even rich carbonates, are submitted to the whole of the above 

 processes by some assayers ; part of the processes are dispensed with by others, aud the 

 rich oxidised ores fused direct for coarse -copper, regulus and calcination. 



Furnace and Implements. A wind-furnace 

 or air-furnace Fig. 533 represents a vertical 

 section of a furnace suitable for assaying 

 copper ores : a, the fire-place, lined with fire- 

 brick, 9 inches square by 12 inches deep; b, the 

 ash-pit; c, flue or stack; d, damper, e, fire- 

 brick covers of two sizes, each clamped with a 

 piece of flat bar-iron ; /, register or iron ash- 

 pit door, provided with a revolving disc of 

 sheet-iron, about 5j inches diameter, having a 

 semicircular opening ; g, the fire-bars of cast- 

 or wrought-iron. The draught is regulated by 

 means of the damper, the register, or by partly 

 removing the fire-brick cover. The fuel used 

 is coke. 



Cornish Crucibles of three sizes, (see ASSAY). 

 Copper scoop, Jiff. 535, 12 inches in length, 4 

 inches in width at the widest part, and l 

 inch at the mouth, provided with a handle 

 about 7% inches in length, for projecting the 

 fluxes into the crucible. Iron mould, fig. 534, 

 having two hemispherical cavities, each If inch 

 in width and -|ths of an inch in depth. Calcining 

 rod, fig. 537, 28 inches in length, inclusive of 

 the blade 4 inches in length. Crucible tongs, 

 fig. 536, represents those used for general assay 

 purposes, those employed by copper assayers 

 are of a different shape and larger dimensions. 

 Flux spoon or ladle, sieves, pestle and mortar, 

 anvil, hammer, chisel, forceps. Balance; it 

 should carry 500 grains, and turn with from ^th to s \th of a grain. Weights ; grain 

 weights are convenient, but special weights are used by copper assayers : the heaviest is 



634 535 536 657 



O 



marked 100, and weighs 400 grains, the unit being subdivided into -J, , , and ^. 

 Fluxes. Those employed are, borax calcined ; glass, green or white, free from oxide 



