IIEFININO OF TI1E recently these have been sold directly to the smelters, save in some mills where they have been reduced on a vaso or lead-bath after an oxidizing roast. Latterly, however, aided by improvements, some of the details of which have been patented by C. A. Stetefeldt, a refinery now in successful operation has been built at the Sloosac mill, belonging to the Daly Mining Co., at Park City, Utah.
The operation consists in : 1. Matting the sulphides in an iron pot ; 2. Roasting the pul verized matter in a muffle-furnace; 3. Dissolving the roasted matter in dilute 4. Crystallizing, CuSO4+ from the solution ; 5. Washing the silver residue, pressing it into cakes, and inciting the cakes into bars. The matting-furnace contains a cast-iron pot 3 ft. 2 in. from the top and 11 in. deep, with a bottom 2 in. thick. This is set in a fireplace and is covered by a hood of sheet-iron. A stove-pipe then connects with the Roessler converter men tioned above. The matte is pulverized in a Brueckner base pulverizer, such as is used in similar work at Mansfeld, Germany. The muffle-furnace in which the roasting is done is oval in shape, 7 ft. long and 4 ft. 6 in. wide, with a cast-iron plate serving as a bottom. The end of the muffle is connected by 4-in. gas-pipe with the Roessler converter. The dissolving tanks are lead lined, and are 3 ft. 6 in. in diameter and 5 ft. 8 in. high. The bottoms are conical, with a dis charge-hole at the end of the cone. A lead pipe allows the heating of the solution by the introduction of steam. The filter-tank below t his last is also lead-lined, and is provided with an asbestos filtering-cloth covered by a perforated lead plate. The crystallizing tanks for + 511,0 are of normal design. The cement copper precipitating tanks have a V shaped bottom, and have grates on which the scrap-iron rests. The tanks are divided into
font- compartments each, through which the solution is circulated by a Korting ejector. At the ends of the tanks are gates through which the cement copper is discharged. A Watson & Stillman hydraulic press, with a mold 6 in. in diameter and 4 in. high, is used to compress the cement silver precipitate. Pure glycerine is used in place of water in the The cakes, after pressing, are dried in a small annular chamber about the chimney of the mat tin g-fn rn ace.
Expenses of the process, when a monthly total of 51 tons is treated, containing 61,950 ozs. of silver and 2,625 lbs. of copper : Labor, $299; coal, 15 tons at $4, $60 ; acid, 4,725 lbs. at cents, $113.40; coke, $15; wear and tear, $30; express and refining charges of 65,210 ozs. bullion .950 fine, $912•95; total expenses, $1,430.25. From this must be deducted the value of the bluestone, $555.95 ; making a net total expense of $874.40, or 1.4 cent per fine oz. of silver.
Works for Reference : The Metallurgy of Silver, by Manuel Eissler, 1889 ; The Metallnrgy of Silver, Gold, and Mercury in the United Stales, by T. Egleston, vol. i, 1887 ; Leaching Gold and Silver Ores, by C. H. Aaron, 1881 ; The Lixiviation of Silver Ores with Hyposulphite Solutions, by C. A. Stetefeldt ; The Lixiviation of Argentiferons Zinc-blende and Galena, by Ottokar Hofmann, Engineering and Mining Journal, February 9, 1883, et seg.; Cupric Chloride and the Russell Extra Solution in Silver Leaching, by C. H. Aaron, ibid., May 11, 1889 ; Trough Lixiviation, by Ottokar Hofmann, ibid., September 10, 1887, et seq. ; Trough Lixiviation, by Ottokar Hofmann, Trans. A. 1. M. E., vol. xvi, 662.
: see Pumps, Reciprocating.
: see Torpedo.
see Coal-Mining Machines and Drills, Rock.