The Thies Chlorinating Barrel (Pig. 4) is a lead-lined iron cylinder, 90 in. in diameter by 60 in. long, provided with suitable journals and driving-pulleys, and with a charging door and test-valve. The capacity of a cylinder of this size is from 1 to 1+ tons of roasted ore. It is designed to make about 15 revolutions per mill. Before charging with roasted ore, suffi cient water is put in the barrel to make an easy-llowing, pulp; from 100 to 125 gals. are used in the 1-ton barrel. If the ore is pure pyrite from 10 to 15 lbs. of chloride of lime anti from 15 to 25 lbs. of sulphuric acid are sufficient to convert all the base metals as well as the gold into chlorides. If the ore contains copper, double the amount of chemicals will be required, and it is considered preferable to divide the chemicals into two portions and add the second after the barrel has been rotated for three or four hours. The time required for the chlorination of a charge of ore is from four to six hours. If at the end of that time the existence of free chlorine in the barrel is shown by moans of the test-valve, the ore is thrown direct on the filter and leached until there is no reaction with ferrous sulphate. The Thies filters are lead lined vats 6 X 8 ft. and 18 in. deep, with a fall of 1 in. toward the outflow. Their bottoms arc covered with perforated glazed tile, on which rests a graded filter-bed of grave], topped off with clean river sand, making a total depth of about 5 in. The thickness of pulp spread on a filter from one toil of roasted ore averages about 4 in., and the time required to leach this ore averages from two to three hours. The precipitating tanks are 8 ft. in diameter and 3 ft. deep. Vats of this size hold solutions from 3 tons of roasted ore.
The Pollok Chlorinating Barrel (Fig. 5) consists of a light steel cylinder supported on trunnions and lined with a coating of gutta-percha about in. thick, on which chlorine has no action. At one end of the cylinder is a valve for charging and discharging. The cylinders arc charged as follows: first, 80 lbs. of nitre is dropped in, then 2 tons of ore, and lastly, GO lbs. of bleaching powder. The charging door is then closed and sealed, and water is forced into the barrel until the pressure rises from 70 to 100 lbs. The cylin
der is then revolved, mixing the ore with the bleaching powder and nitre cake, and the chlorine thus evolved goes into solution in the water, and, acting on the gold, con verts it into chloride. The cylinder is re volved from an hour to an hour and a half, when its contents are discharged on a filter bed placed below. The waste chlorine is blown off and largely recovered by being passed through slaked lime and thus ab sorbed. The filter is made of steel wire lined with India-rubber. The charge, after being decanted on the filter-bed, is filtered, and the chlorine liquor containing the gold is drawn off by a specially designed vacuum pump. by which it is pumped into the pre cipitating tank, where the gold is precipi tated by adding ferrous sulphate. The precipitating tank has a conical-shaped bottom, on which the gold precipitate settles. As soon as the liquor has become clear it is run off, and the gold is removed and melted with borax into bars.
Works for reference: The Metallurgy of Gold, by Manuel Eissler, 1891; The •Metallurgy of Silver, Gold, and Mercury in the United States, by T. Egleston, vol. ii, 1890; Losses in Gold Amalgamation, with _Notes on the Concentration of Gold and Silver Ores, by Walter McDermott and P. W. Duffield, 1890; Gold, its Occurrence and Extraction, by A. G. Lock, 1882; Practical Gold-Yining, by C. G. W. Lock. 1839; -Votes on the Treatment of Gold Ores, by F. O'Driseoll, 1889; Leaching of Gold and Silver Ores, by C. H. Aaron. 1881; Notes on the Hydro-metallurgy of Gold and Silver, by C. H. Aaron, Annual Report of the State Min eralogist of California, 1888: Gold-Milling in the Black Hills, by II. 0. Daman, Tmasae lima American Institute of Mining Engineers, vol. xvii: The Thies Process of treating Low Grade Auriferous Sulphides at the Haile Nine, South Carolina, by A. Thies and William B. Phillips, ibid., six. 601; The Practical Chlorination of Gold Ores and the Precipitation of Gold from Solution, by John E. Bothwell, Engineering and _Mining Journal, vol. li, 165; Notes on Gold-Milling, by C. II. Aaron, vol. xlviii, August 10 and 17, 1889.