COPPER.

329

o 24 hours, according to the degree of purity of the crude copper. The temperaturesucmiti be graduated, in order that the oxydizement may have time to complete, and thatTh V ? . substances which the copper still retains .may escape in the gaseous form,lhe fusion must take place only towards the end of the operation.

. c harge varies from a ton and a quarter to a ton and a half. The metal obtained*s run out into moulds of sand. It is covered with black blisters, like steel of cementation;whence it has got the name of blistered copper. In the interior of these pigs, the copperpresents a. porous texture, occasioned by the ebullition produced by the escape of thegases during the moulding. The copper being now almost entirely purged from thesulphur, iron, and the other substances with which it was combined, is in a fit slate to beennea. This operation affords some scorise; they are very heavy, and contain a great°xyde of copper, sometimes even metallic copper.

•these scoriae, as well as those of the third melting and of the refining, are added to theccond fusion, as we have alreidy stated, in describing the fourth operation,la some works, the roasting is repeated several times upon the blue metal 3 in order torin g it to a state fit for refining. We shall afterwards notice this modification of the

treatment.

_ Eighth operation. Refining or toughening . —The pigs of copper intended for refiningis VP on J be so ^ e the refining furnace through the door in the side. A slight heatnrst given, to finish the roasting or oxydation, in case this operation has not alreadyof C fi ^ Us ^ e( ^ f ar enough. The fire is to be increased by slow degrees, so that, by the endhe t - h ° Urs > *be C0 PP er may begin to fiow. When all the metal is melted, and when therah 1S Cons iderable, the workman lifts up the door in the front, and withdraws with ae th e few scoriae which may cover the copper bath. They are red, lamellated, veryaad closely resemble proloxyde of copper.

vice 16 ie ^ ner ta kes then an assay with a small ladle, and when it cools, breaks it in abath to . See *be state of the copper. From the appearance of the assay, the aspect of theq u ’ r e state of the fire, &c., he judges if he may proceed to the toughening, and what0r . Hy of wooden spars and wood charcoal he must add to render the metal malleable,refirf ^ an s ua " e of the smelters, bring it to the proper pitch. When the operation ofIts begins, the copper is brittle or dry, and of a deep red color approaching to purple.

^ o aia is coarse, open, and somewhat crystalline.

^nd ^ Xecute the refining, the surface of the metal is covered over with wood charcoal,' v ood " rer * about with a spar or rod of birch wood. The gases which escape from theso that 0 ? 8 * 011 a brisk effervescence. More wood charcoal is added from time to time,bailed • SUl 'face of the metal may be always covered with it, and the stirring is con-by t j )e Wlt h the rods, till the operation of refining be finished, a circumstance indicatedand its a T s taken in succession. The grain of the copper becomes finer and finer,

the trial* 01 ' brightens. When the grain is extremely fine, or closed , when

c °Pper •^ l p Ces > half cut through and then broken, present a silky fracture, and when theVer ifies IS f°/i a ^ lne bgbt red, the refiner considers the operation to be completed ; but hepose, he t I f urt her the purity of the copper, by trying its malleability. For this pur-Co Pper F a \ e . s . out a sample in his small ladle, and pours it into a mould. When thedo es not'* So , but still red-hot, he forges it. If it is soft under the hammer, if itit to b e - Cr .* °n the edges, the refiner is satisfied with its ductility, and he pronouncesCo Pper out P ro P er state. He orders the workmen to mould it; who then lift the°fthe si Ze ° • l ^ e ^* urn ace in large iron ladles lined with clay, and pour it into moulds° r bigs arp S ?o taWe to tlie demands of commerce. The ordinary dimensions of the ingotsThe p er j T* iac hes broad, 18 long, and from 2 to 2J thick.

Offers a 1**° i° re fi n i n S process is 20 hours. In the first six, the metal beats, and*be poi nt ° , roa sting ; at the end of this time it melts. It takes four hours to reachb r °cess lasts ^ lca *be refining, properly speaking, begins; and this last part of thel be ingots a *i , out ^ hours. Finally, 6 hours are required to arrange the moulds, cast

T heeha r ? e lll r ettllerUrrlacecooL

• copper in the refining process depends upon the dimensions of the fur-*£, a tons; and'th WOr ^ Sj one °^* l * ie most important in England, the charge varies from• consumnt* ^ Uaxit ity of pure copper manufactured in a week is from 40 to 50 tons.a Pi?s. b l0n ^cl is from 15 to 18 parts of coal, for one part of refined copper. ’’hen the

ox , metal* 5 °? ers difficulties in the refining, a few pounds of lead are added to0 Mati° n 0 p t , > y tlle facility with which it scorifies, acts as a purifier, aiding the?ht to ho , . on an n Other metals Hint mav he nresent in t.hr» rnnner. The lead

„ .. tron and othei metis th* «

«»?ht to be added immediately after removing the „ 0 ssible surface to the action^ ^should be constantly stirred up, to expose the grea P for (he sma llest q uan yair > and to produce the complete oxydation of the i >

metal allmio.i -• . ■

scale

“* capper, is difficult to clear up" in the lamination; that is to say,x 5de doegnot come cleanly from the surface of the sheets.

the