ijo 'New Method ofextraBing Silver from 



the tejl (heerd) and itAJlrJl wafle * (abzug) need not be reduced to the rcguHne ftate by 

 a feparate operation ; becaufe this may be done at the fame time, that another portion of 

 copper-mat is cleared of its filver by fufing them together with it. iBut as this perfedion 

 of any art can only be obtained by experience, and difpatch in the manipulations can be • 

 acquired by pra£lice alone, it will be found neceflary, even in this inftance, to perform 

 repeated experiments, for the purpofe of afcertaining- the beft dimenfions of the parts of 

 the furnace, the mod fuitable proportion of the quantity of coals to be employed, and the 

 mofl: advantageous direftion of the bellows pipe ; as well as the mod convenient regulation 

 of the blaft, and the moft fuitable proportion of the copper-mat to the lead to be em- 

 ployed in this procefs. 



The advantages afforded by my method, compared with thofe refulting from the pro- 

 cefs of eliquation, are evident. No lead is here loft by combuftion, becaufe it is accurately 

 covered by the copper-mat, and no intenfc heat is required, becaufe thefe fubftances are of 

 eafy fufion. A much fmaller quantity of lead is alfo fufficient in this procefs, than in that 

 of eliquation ; perhaps only a fifth part, or ftill lefs ; whence, upon the whole, the lofs or 

 wafte of lead, including the cupellation, is confiderably lefs. Befides this, my procefs 

 requires but little expence in the building or apparatus, and the expences of fmelting are by- 

 this means in part compenfated ; feveral fires for roafting the copper-mat being rendered 

 unneceflary, and thus faved. From this diminution of expences in niy new method, fuch 

 copper-mats may like wife be dcpriwd of their filver, as when worked into black copper arc 

 fo poor in filver, as niot to repay 'he charges of eliquation. 



3y thefe means, therefore, when the quantity of fufed copper-mat in the furnace A has 

 fu'IEciently increafed, it will reach the communicating aperture {a), after having driven 

 before it all the lead into the outward-hearth. Laftly, as foon as the copper-mat has ad- 

 vanced to beneath the furface of the lead in the outward-hearth B, it will rife through the 

 lead by the laws of hydroftatics, and penetrating its mafs, will place itfelf on the 

 furface of the lead, continually accumulating there, until having reached the proper height, 

 it can run offthroBgh the indentation cut in the rim of the fore-hearth. 



In this fimple manner, therefore, any required quantity of copper-mat may, by repeated 

 charging of the furnace, pafs through a determined quantity of lead ; and may be thus de- 

 prived of its filver without lofs in burned lead, and the lead itfelf may at pleafure be more 

 orlefs impregnated with filver. 



Experiments in the frnall Way, to confirm the Succefs of this Method. 



In order to perform thefe operations in the fmall way, as well to confirm tlie theory 

 mnd praftice, and at flie fame time to difcover a method of making the neceflary ex- 

 periments which might enfure correfpondent performancc'in the large way, I proceeded 

 lu the following manner : 



• FWfi 'waftt is the drofs or fcoria formed in the firft part of the operation, when the cupelling is per- 

 formed in the large way in the refining furnace. Sec Gren'i Principles of Cbem, §. i4g6."-Tranfl. 



A Heflfian 



