108 Zijic Desilverization. 



silver bullion produced weighs about 9000 oz. and is usually 990 

 to 995 fine, and contains both silver and gold, the proportions 

 of both metals' varying with the bullion or ore purchased. The 

 litharges produced are reduced in a reverberatory furnace. 



At Mansfield Valley, the cupelle is made of the best hydraulic 

 Portland cement, moistened enough to ball in the hand, and 

 stamped in an iron mould. The tf st is three by four feet on the 

 inside. The iron frame which supports it is flanged on the bot- 

 tom at right angles to the rim, wliicli is 7i inches high, while the 

 flange is b\ wide. The test is made either on an iron mould, 

 which gives the shape to the inside, or is cut out of the material 

 after the frame has been stamped full. At first they were always 

 cut out, now they are generally stamped over the mould. When 

 made, the cupelles are left to temper for four weeks, to insure a 

 good test. They could be used after a week, but it is better not 

 to do so. The test is supported in the furnace on an iron plate, 

 and is held op to its place by four large screws. The charge of 

 a rich alloy is 1400 lbs. The cupelle is used a week, and cupelles 

 from ten to twelve tons up to 996 fine, and that directly from 

 the lead. The lead is added in the cupelle till just before it is 

 too rich, then cleaned off and the silver is refined, and is run 

 into the brick moulds directly from the cupelle. A little copper 

 is added, to prevent the spitting of the silver. The copper 

 absorbs the oxygen, and prevents the spitting. When any cop- 

 per is present in the lead, even when gold is present, it rarely 

 ever- spits. When the silver is ready to cast into bricks, the test 

 is loosened, and a curved bar is placed on a support made for the 

 purpose underneath it. The whole test is then ra sed, and the 

 silver, tipped at once into the moulds for the bricks, is 994 to 996 

 fine. This cupelle thus allows of casting, without refining in 

 a separate furnace. It is the invention of Mr. Enrich, the 

 manager of the Pennsylvania Lead Works, and is one of the 

 many ingenious additions to metallurgical progress which he 

 has made. 



The following tables, prepared by Mr. E. F. Eurich, give the results of 

 cupellation at Mansfield : — * 



* Mining Commissioners' Report for 1875. 



