The largest chlorination works in the world are at the famous Mount Morgan mine in New Zealand, where a modification of the Newberry-Vantin process of barrel chlorination is used. The ore averaged, as worked, 5 oz. gold per ton, and 1,800 tons were treated per week, while the tailings are said to contain only 3 dwt. gold per ton, which, if correct, represents a saving of 07 per cent. The cost of the process on this large scale is given as $7.50 per ton. Mr. A. Thies states that the cost of chlorinating at the Haile Mine, Lancaster County, North Carolina, is $'4.621 per ton of roasted ore, divided as follows: Roasting, $2.62i ; chlorinating (power, 12i cents ; labor, 95 cents ; chemicals, 60 cents), g1.671-; ferrous sulphate for precipitat ing, 121 cents; repairs and wear, :20 cents; total, $4.62-i. This is equivalent to $3.47 per ton of raw pyrites. No figures have been published concerning the cost of chlorination in the Black Hills, but the II idle figures have probably been exceeded, owing to the larger tonnage worked, notwithstanding the higher cost of labor, fuel, and supplies.
.AsAutANAToRs.—A large variety of mechanical amalgamators, to take the place of cop per plates, have been invented, but none have come into very general use. These. ma chines are generally pans or cylinders in which the pulp is rotated with mercury, the object being to bring the particles of gold in more intimate contact with the mercury than on the plates.
Jordan's Centrifugal Amalgamator (Figs. 1, 2) consists of a series of shallow dishes, attached one below another to a central revolving shaft, and inclosed in a fixed circular casing. Secured to the inner side of the cas ing, and alternating with the dishes, are slightly inclined shelves, also amalgamated. The pulp fed into the amal gamator enters the first dish, in which it is revolved until impelled by the centrifugal motion over the edge of a dish. It then falls on one of
the shelves and is thus con veyed to the center of the second dish, there to under go similar treatment. This is repeated to the end of the series, where the tailings es cape. The free gold and sil ver contained in the pulp are arrested by the amalgamated . dishes and shelves, which are scraped at suitable intervals and the amalgam retorted.
The Cook Amalgamator (Fig. 3) consists of a horizon tal iron cylinder A, with an interior spiral rib, rotated about 30 times per min. The spirals e form a channel 40 ft. long, which divide the material and keep it divided all the way through the cylinder. The ro tating action spreads the pulp and subjects it to a rolling motion in the water, the g,angue going ahead of mineral A- of the distance over amalgamating surface E, and g over non-amalga mating surface e, which al ways holds enough mercury to coat or amalgamate free min eral, nicking the whole dis tance amalgamating with only amalgamating surface. The mineral is separated from the gangue. amalgamated and col lected into little hunches of amalgam in cylinder, and as amalgam passes to the tables and wells. The tables have a continuous amalgamating surface to the mercury-wells where the amalgam is col lected. Gate h spreads the water. etc., which passes under it and flows up from gate-well and is thrown down by splash plate he on table II. thence on to tailings indicator J and discharge-spout o. The tailing-indicator consists of two amalga mating plates on which the tailings drop ; these plates indicate, collect, and deposit, it is said, in the well any possible loss of amalgam or mercury from the machine. According to the manufacturers, a cylinder 7 ft. long and 2 ft. in diameter will treat the pulp of from 5 to 10 stamps. It requires 18 gals. of water per min., and + horse-power.