926 COPPER 



7. Refining the blister-copper. This is effected either in the German hearth by the 

 action of glowing charcoal and a highly-inclined blast, and the fine-copper obtained in 

 the form of rosettes ; or the Welsh reverberatory furnace is employed, and the copper 

 cast into ingots. For extraction of silver from the Mansfield copper regulus, see 

 SILVER. 



Figs. 518, 519, 520, represent the reverberatory furnace generally employed in 

 the Harz, in the district of Mansfeld, Saxony, Hungary, &c., for the treatment of black 

 copper, and for refining rosette copper upon the great scale. An analogous furnace is 

 used at Andreasberg for the liquefaction or purification of the matts, and for workable 

 lead when it is much loaded with arsenic. 



Fig. 518 presents the elevation of the furnace parallel to the line i K, of the plan 

 fig. 519, which plan is taken at the level of the tuyere n of fig. 520 ; fig. 520 is a 

 vertical section in the line L M, fig. 519. k represents one of two basins of reception, 

 brasqued with clay and charcoal ; n n, two tuyeres through which enters the blast of 

 two pairs of bellows ; q, door by which the matter to bo melted is laid upon the solo 

 of the furnace ; v, v, two points where the sole is perforated, when necessary to run 

 off the melted matter into either of the basins k ; x, door through which the slags or 

 cinders floating upon the surface of the melted metal are raked out ; y, door of the 

 fire-place. The fuel is laid upon a grate above an ash-pit, and below the arch of a 

 reverberatory, which is contiguous to the dome or cap of the furnace properly so called. 

 In the section,^. 520, the following parts may be noted: 1, 2, 3, mason-work of the 

 foundation ; 4, vapour-channels or conduits, for the escape of the humidity ; 5, bed of 

 clay ; 6, brasque, composed of clay and charcoal, which forms the concavity of the 

 hearth. 



Figs. 521, 522, 523, show the furnace formerly employed for liquation in one of 



the principal smelting works of the Harz. Fig. 623 exhibits the working area charged 

 with the liquation cakes and charcoal, supported by sheets of wrought-iron ; Fig. 

 521 is the plan, in the line F G, of fig. 522. 



A liquation cake is composed of 



Black copper holding at least 5 or 6 Loths (2| or 3 oz.) of silver per cwt., and 

 weighing 90 to 96 Ibs. Lead obtained from litharge, 2 cwts. Litharge, cwt. 



From 30 to 32 cakes are successively worked in one operation, which lasts about 

 4 hours ; the furnace is brought into action as usual, with the aid of slags ; then a little 

 litharge is added ; when the lead begins to flow, the copper is introduced, and when 

 the copper flows, lead is added, so that the mixture of the metals may be effected in 

 the best possible way. 



From 8 to 16 of these cakes (pains) are usually placed in the liquation furnace, 

 figs. 521, 522, 523. The operation lasts 3 or 4 hours, in which time about 1 quintal 

 of charcoal is consumed. The cakes are covered with burning charcoal supported, as 

 before stated, by the iron plates. The workable lead obtained flows off towards the 

 basin in front of the furnace ; whence it is laded out into moulds set alongside. (See 

 fig. 518). If the lead thus obtained be not sufficiently rich in silver to be worth 

 cupellation, it is employed to form new liquation cakes. When it contains from 5 to 

 6 Loths of silver per cwt., it is submitted to cupellation in the said smelting works. 

 See SHVEB. 



The refining of the eliquated copper (called Darriinge) from which the silver has 

 been sweated out by means of lead, can be performed only in small hearths. The 

 following is the representation of such a furnace, called in German Kupfergahrheerd. 

 Fig. 524 is the section lengthwise ; fig. 525 is the section across ; and fig. 526 is 

 the ground plan : in these figures a is the hearth-hollow ; b, a massive wall ; c, 

 the mass out of which the hearth is formed ; d, cast-iron plates covering the hearth; 



