ORE DRESSING AND MILLING (PART 4) AMALGAMATION SILVER AMALGAMATION BOSS-PROCESS MILL 1. Boss Continuous Process.-The Boss continuous process for the amalgamation of silver ores is a comparatively new process, which will in time probably supersede all the older processes. The adoption of the Boss system eliminates a considerable portion of the hand labor ordinarily required about a silver mill. The operation is entirely continuous, and, except where the ore requires roasting, it need not be handled from the time it is fed into the stamps until the mineral and amalgam are cleaned out of the settlers. When the ore is roasted, the pulp from the stamps (crushed dry) is conveyed to a roasting furnace, and from there to the cooling floor, where it is spread out and allowed to cool before charging into the grinding pans, in which the ore is mixed with water and ground to the proper fineness before entering the amalgamating pans. A Boss-process mill section is shown in Fig. 7. 2. Grinding Pans.-The grinding for this process is done in small iron pans 4 feet in diameter and 1 foot 4 inches For notice of copyright, see page immediately following the title page. deep, constructed somewhat similarly to the grinding and amalgamating pans previously described. The driving arrangement is the same as that used on the Boss amalgamating pans, with this exception: there is a compressed spring in a sleeve around the muller nut, which keeps the adjusting screw pressed down firmly on the spindles. The muller ring and driving cone are cast in one piece. The ring is a flat, vertical rim, connected to the cone by horizontal spokes, and the shoe is bolted to lugs projecting outwards from the sides of the rim, opposite the ends of the spokes. The upper edge of the rim is turned inwards at right angles, forming a flat, horizontal flange, or lip, about 5 inches wide. The shoes and dies are both solid, flat rings, but have oblique slots on their inner edges, extending a short distance into the rings, in order to get the same effect of suction that is obtained when the shoes are in segments, with oblique slots between them. The pulp is fed into the muller ring, and is obliged to pass under the muller in order to get to the outside of the pan, since the joint between the muller ring and the shoe is made water-tight by a rubber gasket, and the flange at the top of the ring prevents the pulp from splashing over the sides and turns it back to the middle of the pan. Grinders are usually placed in pairs, two for each ten stamps, one being set slightly lower than the other. The pulp from the entire ten stamps passes into the first pan, where it is ground; thence it passes on into the second pan, where it is still further ground; from here it discharges into the first amalgamators-or in some mills into a chemical mixer, which is interposed between the grinders and the amalgamators, and in which the chemicals are mixed with the ore before it enters the pans. The grinding pans are on a higher level than the amalgamators, and behind them, and are driven by friction clutches on a separate shaft, the clutches being thrown in and out of gear by levers operated from the pan floor. 3. The amalgamating pans used in the Boss process are described in Art. 58, Ore Dressing and Milling, Part 3. The number of pans in the series depends both on the capacity of the mill and on the character of the ore. Thus, the greater the capacity of the mill, the larger must be the number of pans in the series, since the ore must be in the pans a certain length of time in order to obtain a good percentage of amalgamation. As the operation of the mill is perfectly continuous and all the pulp has to pass through every one of the pans in the series, the greater the quantity of pulp, the less time it will be in each pan; consequently, if the amount of ore handled by the mill is increased, the number of pans in the series must be increased proportionately, in order to have the material exposed to the action of the mercury for the proper length of time. Or, again, if one ore amalgamates more readily than another, it will require less time in the amalgamating pans, and allowing both ores the same time in each pan, the first would require fewer pans in the series to treat the same amount of pulp than the second. The same is true of the settlers. The pans. settlers, and-when one is used-the chemical mixer are all in the same line and on the same level and are driven from the same shaft, each machine being thrown in or out of gear independently of the rest by means of the friction clutches shown in the illustration of the pan in Fig. 21, Ore Dressing and Milling, Part 3. To avoid the necessity of stopping the whole mill when pans are cut out for cleaning or repairs, steam siphons are used, which carry the pulp past the idle pans and into the next pans beyond them, and the operation of the mill proceeds without interruption. The shaft is made in sections— one section to each pan-coupled together. Every other coupling is a clutch coupling and the rest are ordinary flange couplings. Between the faces of each flange coupling a ring or washer is inserted, the thickness of which is a trifle greater than the distance it would be necessary to draw the two portions of the clutch coupling apart in order to disengage them. When it is necessary to remove any section of shafting, the cover of the shaft box is removed, the flange coupling at one end is unbolted, the washer |