This section is from the book "Leaching Gold and Silver Ores. The Plattner And Kiss Processes: A Practical Treatise", by Charles Howard Aaron. Also available from Amazon: Leaching Gold And Silver Ores.
54. Suction Pipe. In cases of difficult leaching, filtration may be facilitated by means of a suction pipe. This is simply the discharge pipe of the leaching vat, made of stiff hose, or of wood, instead of soft rubber as in other cases, and extended to a vertical depth of from six to twenty-five feet. The hose, near its lower end, is coiled once around, as in the accompanying diagram, and secured by a piece of wire; or, a re-curved piece of lead pipe may be inserted in the end of the discharge pipe, or again, the end may be immersed in a cup of water, although this plan is less convenient than the others. The object, in either case, is to prevent the entrance of air.
55. Vent Pipe. Though not the general practice, it is well to have a vent pipe to prevent disturbance of the filter by the air or gas beneath it, when displaced by the entrance of water, especially if the discharge pipe is hung up, closed as in the case of using suction, or occupied by the introduction of water below the filter, as in commencing the washing of silver ore. There are several methods of arranging a vent pipe. Perhaps the simplest is the following, represented by a dotted line in the preceding diagram.
When the ore vat is disconnected from the chlorine pipe a short piece of rubber tube is connected at one end with the nipple through which the chlorine was introduced, and at the other with the upper part of the vat, by being inserted tightly in a hole bored through the side, just below the cover. The short tube may be left permanently on the lead nipple, and connected with the chlorine pipe when required, by means of a short piece of lead pipe, which afterwards serves also for connecting the tube with the hole in the vat side.
Suction and Vent Pipes.
Whether water be introduced from above or below the ore, the air or gas beneath the filter will pass through the tube, and return to the vat above the ore. If the chlorine nipple is to be used thus as a vent, it should be set in as high as possible, consistently with the delivery of the chlorine below the filter. A special vent pipe may be made by boring a one-quarter inch hole lengthwise through a strip of wood, and attaching the strip to the inside of the vat by means of wooden pins. It should terminate at one end immediately below the vat cover, and at the other, beneath the burlap on the gravel. The upper end must be plugged, and a transverse hole bored to connect with the vertical passage. This aperture must be plugged during the chlorination, and opened when water is admitted.
56. Sieve. This is made of stout brass wire, and has from four to eight meshes to the running inch. It is of an oblong form, about two feet wide by three feet long, and is framed with wood. The sides are six inches high, and are prolonged so as to form handles at one end, like those of a wheelbarrow, and at the other points of attachment for suspension ropes from a support above. It is operated by hand, being swung back and forth, directly over the vat which is in course of being charged, into which the ore which passes through falls, in a loose and open condition, while the lumps are retained.