176 Mr. H. L. Pjttinson on Smelting Lead Ore, §c. 



reducing is about 4A Winchester bushels, or near 3^cwt. per fodder of 

 Lead reduced, including the quantity mixed with the Litharge. 



The quantity of Test-bottom and Litharge Slag Lead made in refining 

 may be variable ; but, in several cases which have come under the 

 writer's notice, they have, together, amounted to one thirty-second 

 part of the original Lead refined. 



The produce of Lead from the refiner's fume, treated as described 

 in page 40, has appeared to be, in the only case submitted to the writer's 

 consideration, about 1 per cent, on the total quantity of Lead under- 

 going the refining process ; but this deposit must be very much modi- 

 fied, like the hearth ends and smelter's fume, by the degree of heat at 

 which the refining furnaces are worked, it is therefore impossible, per- 

 haps, to make a statement which will exactly correspond with experience 

 at every smelting establishment. 



CORRESPONDENCE OF THE PRODUCE OF SILVER WITH THE 

 ASSAY, AND LOSS OF LEAD IN THE PROCESS OF REFINING. 



The practice is very general of assaying the Lead to be refined previous 

 to the process, by taking a chip from each pig, melting the whole together, 

 and submitting a known weight to cupellation. It frequently happens 

 that the quantity of Silver obtained in the large way, is greater than that 

 indicated by the assay, the reason of which is, that the Litharge, as it 

 sinks into the small cupel, carries with it a minute portion of Silver, ren- 

 dering the button obtained rather less than it ought to be ; but, by re- 

 ducing the Litharge absorbed by the small cupel back into Lead, with 

 Black Flux and Borax, and refining this Lead a second time, another 

 minute button of Silver is obtained, which added to the first button, 

 generally indicates a quantity of Silver in the lead under examination, 

 With which its produce in the great way, when carefully refined, very 

 closely coincides, taking into account the small portion of Silver un- 

 avoidably carried over with the Litharge, and found in all samples of 

 refined Lead, to the extent of from half an ounce to an ounce per fod- 

 der. It will easily be conceived that if the small process of cupellation 

 has been carefully performed at first, with a due degree of heat and in 



