COPPER.
33ft
rnshwood and charcoal; a process which requires from 7 to 8 weeks. The product ofsl ^-fold calcination is the Gahrrost of the Germans (done and purified); it has acolor like red copper ore, varying from blue gray into cochineal red; a granular frac-ture ; it contains a little of the metal, and may be immediately reduced into metalliccopper, called kupfermachen. But before smelting the mass, it is lixiviated with water,to extract from it the soluble sulphate, which is concentrated in lead pans, and crys-tallized.
The lixiviated gahrbste mixed with from J to J- of the lixiviated dimnsteinrost, and J, to J?f the copper slate slag, are smelted with charcoal or coke fuel in the course of 24 > hours,ln a mass of 60 or 80 cwts. The product is black copper, to the amount of about J theWeight, and 1 of diinnstein or thin matle. This black copper contains in the cwt. from12 to 20 loths (6 to 10 oz.) of silver. .The diinnstein consists of from 60 to 70 per cent.01 copper combined with sulphur, sulphuret of iron, and arsenic;, and when thricejP as ); e( l> yields a portion of metal. The black copper lies undermost in the crucible ofe furnace; above it is the diinnstein, covered with the stone slag, or copper cinder,csulting from the slate-smelling. The slags being raked off, and the crucible sufficientlybr f T e or nozzle hole is shut, the diinnstein removed by cooling the surface and
tak inMack
tng the crust, which is about J to J inch thick. The same method is adopted for
S out the black copper in successive layers. For the de-silvering of this and similar
312
Fig. 312 is a vertical sectionthrough the form or tuyere inthe dotted line a b of fig. 314.Fig. 313 is a vertical section inthe dotted line c d of fig. 31 6. ais the shaft of the furnace, b therest, c c the forms; d the sole orhearth-stone, which has a slopeof 3 inches towards the frontwall; e e, &c. casing walls of firebricks; f /, &c. filling up wallsbuilt of rubbish stones ; g g a_mass through which the heat isslowly conducted; 7i h the twoholes through one or other ofwhich alternately the product ofthe smelting process is run offinto the fore-hearth. Beneaththe hearth-sole there is a solidbody of loam; and the fore-hearth is formed with a mixtureof coal-dust and clay; k is the^ discharge outlet. Fig. 314 is ahorizontal section of the furnacethrough the hole or eye in thedotted line e f of fig. 312; fig.315, a horizontal section of theshaft of the furnace through the
_ , u [n . __ „ _ The height of the shaft, from the line
fr ° m that I? ^ feet ! from e to g, 25 inches; from c to the line below b , 2 feet;a hd at c or 11 - 6 ^‘ ne opposite g g, 2 feet. The width at the line g g is 3 feet 3 inches,The fefin^a es ' ^ lle baslns * hfig■ 314, are 3 feet diameter, and 20 inches deep.'s °tne account C0 PPer is said to be well executed at Seville, in Spain ; and', therefore,The first oh' mo ^ e operating there may be acceptable to the reader.sac h as sulnh * s to eva porate in a reverberatory furnace all the volatile substances,lr e second enie ) antlmon y) &c., which may be associated with the sulphur; and
&C- > with the i Xydlze aa(1 to convert into scorise the fixed substances, such as iron, lead,y et which res' f ast P° ss ^Me expense and waste. The minute quantities of gold and sil-’ s Usually tnade S - ox ^ at *°n cannot be in any way injurious to the copper. The hearthchimes, and w 0 a re fr a ptory sand and clay with ground charcoal, each mixed in equaleat firmly intoThc ^ * nto a doughy consistence with water. This composition isto bq f ar , furnace bottom. But a quartzose hearth is found to answer better,rfofore kindling ^ a ^? e ’ suc ^ as a tied of fire-sandstone.
RfPoed mhtnro” furnace, its inner surface is smeared over with a cream-con-ce ■ e ca st Pi™ ° f , fire-day and water.
SslVe layer °crn« r ' ° ( ^ <s Mack or crude copper, are piled upon the hearth, each suc-Sln " at right angles the layer beneath it, in aider that the flame may .
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® P to the” hne g h of figs. 312 and 313.