Zinc Dcsi/t'ci-izafio/K t)l 



small amount of material is collected, and this very near the 

 furnace. It contains only from 3 to 4 oz. of silver. The other 

 Grasses are treated in a reverberatory furnace. The materials 

 being at first only partially reduced, the first lead which flows 

 carries most of the silver and is put to one side. The charge is 

 then completely reduced. The product is a very hard lead, 

 which is allowed to accumulate until there is enough to make a 

 charge in the softening-furnace. 



If the ores contain a very large amount of antimony, there 

 will be two or three sets of crasses after those containing copper 

 have been removed, which will be mostly very impure litharges. 

 The lead produced, frolm them is a compound of arsenic and an- 

 timony, which is not refined, but sold as hard metal. The loss 

 in lead in softening is about 2] per cent. 



2. Incorporation of the Zinc, and Separation of tlie Zinc 

 Scums. — To effect the desilverization, there are at Cheltenham 

 three kettles, set in a triangle, at Mansfield Valley a series of 

 three kettles set in a row, and at the Germania Works, a series 

 of five, set as shown in Fig. 4, the first two holding 20 tons 

 each ; the next two, 7 tons, and the last, 4 tons. These kettles 

 are set in masonry, with a fire-place underneath them. The 

 furnace is tapped into the two upj^er ones alternately. The 

 upper kettles at Mansfield hold 23 tons. The upper kettles at 

 Cheltenham weigh 4,700 lbs. each, and cost between $400 and 

 1500 each. They are 6 feet 6 inches in diameter, and 3 feet deep. 



At the Germania Works, the discharge-S]30ut is cast on the 

 bottom of the kettles, and is constantly breaking. At Mans- 

 field, the middle one has a spout at the bottom, which com- 

 municates with the third and smallest. These kettles are 

 filled with melted lead from the softening-furnaces. When 

 they are full, they are heated up to the melting-point of zinc, 

 which takes about one hour. It is important that the heat should 

 be high enough to melt the zinc readily. The kettle is so large that 

 there is but little danger of over-heating. When the tempera- 

 ture is at the right point, the zinc is added. At the Germania 

 Works and at Mansfield, the zinc is thrown in or laid on the top 

 of the lead, and incorporated as it melts. At Cheltenham, it is 

 placed in an iron cage, which is let down to the bottom of the pot. 

 The amount of zinc to be added will generally be about one pound 



