Arizona weekly miner., 1874-06-05
REFINING.
Separation of Gold and SAoer from Leod.

Separation of Gold and SitCer from Leod.
 But little is known, by those not engaged in the business of the methods employed in this eoun- try for separating gold and silver from impure lead; and we believe the following facts, gath cred by our reporters, will be found of interest
 Two grades of impure lead are imported from Utah to Easterl States for refining. The impur- ites are gold and silver, which communicate n superior hardness to the lead, and also increase it's Instability. These ingredients, however, do not exist in sufficient proportion to warrant the application of the cupel process, or rather the loss of lead would be so great as to make the op- eration too expensive. The lowest grade con tains so ounces of silver and one of gold to the ton; the other grade, known as the R. c. M bull lion contains 120 ounces of silver and of gold per ton of bullion. Besides these components, certain proportions of antimony and occasionally trace of arsenic enter into the composition of the bullion.
 The bullion is first placed in kettles and melted to refine it. In this process the dross, which ris- es to the surface of the metal during the melting, contains the greater part of the impurities, such as antmony, bismuth, etc. This dross is after ward refined separately in an appropriate furnace. This having been removed, the melted metal is drawn of into a larger kettle. It is thence re- moved to other kettles, and a certain proportion of zinc added, the quantity bearing fixed ratio 10 the quantity of silver already in the metal. In the working of each sample of bullion preim- mary assay is necessary to determine the prOpor- ton of silver.
 When the metal is melted with the zinc, slow fire is employed; and, as the process goes on, an alloy of silver and zinc rises to the surface The latter is skinned off and placed in a plumbago crucible, provided with neck similar to a retort. The crucbe is then placed in one of Du Faurs furnaces, which is so arranged that it can be til- ted by the aid of wheel attached to the furnace. The zinc is here distilled off, and condenses in the tube or neck, which is attached to the cruel be. \ part of the zinc is driven off as oxide, and this is lost, but about two-thirds of it sub- lines in the neck of the cruicible. When the tuhe iS removed the zinc is withdrawn therefrom, and used in a similar operation. It will be re- membered that silver melts at about the same temperature at which zinc is vOatalized.
 The metal remaining in the crucible consists of gold silver and lead, the latter in small quantity. This having been withdrawn, the precious metals are separated from the lead ny eupeation. The resulting gold and silver then run into ingots, and the silver removed by nitric acid, or by what ever method may be most convenient. In this mixture of gold and silver. gold forms from one- half and one-half per cent. Some idea of the magnitude of the operation may be formed from the following facts regarding large estab- lishment. They claim weekly production of silver of about 12, 900 ounces, and a proportion ate quantity Of lead. Generally, the process re- turns about S9 per cent. of the lead which was in inc bullion at the commencement of the opera ton. They use cast iron kettles in the proces Of separating the silver from the lead by the aid of zinc, each capable of holding two tons of bullion. Twelve of Du Faur's tiltng furnaces are used, two capable of q charge of six tons each, one of twelve tons, and one of sixteen tons.-lSalt Lake Tribune.