The metallurgy of silver and lead; a description of the ores: their assay and treatment, and valuable constituents

9781130382990: The metallurgy of silver and lead; a description of the ores: their assay and treatment, and valuable constituents
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1874 Excerpt: ...Its circumference consists of a strong wroughtiron ring, nearly elliptic in shape, and with a framework of iron bars across the bottom, as shown by the dotted lines in fig. 71. This iron periphery is known as the test ring. In order to prepare the cupel, this frame is beaten full of finely-powdered bone-ash that has been moistened with water in which a small quantity of the carbonate of potash has been dissolved. The hollow shown at b is carefully and regularly shaped with a trowel, until the bottom remains about one inch thick above the iron bars, 1111. The opening, L, fig. 69, serves to introduce into the hearth the rich lead which has previously been fused in a kettle near the furnace, and the door, o, allows the litharge to flow from the hearth into the pots placed in front to receive it. The fire-place, a, is 15 inches by 4 feet, the fire-bridge, b, 30 inches long, the chimney, P, 10 inches square. The blast thrown in through the tuyere at w, is arranged to introduce from 18 to 20 lbs. of air per minute. MANIPULATION IN CUPELLING RICH LEAD BY THE ENGLISH METHOD. The cupel, after having been formed as above described, is dried for several days, and then introduced beneath the arch, B, and wedged firmly in its place. The coal fire is lighted in the fire-place, a, and the furnace heated very carefully, lest the cupel should crack. When the temperature reaches a dark red, lead which is kept fused in a kettle near by, is poured into the cupel, H, by means of a long-handled ladle, the blast is put on, and the fire raised until the lead reaches a bright red heat. The formation of the litharge takes place rapidly, and as fast as produced it is allowed to run off through a channel in the cupel, which is kept at a constant depth. As the lead is oxidised, and its...

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