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.
175. Some operators use wooden faucets for this purpose. One objection to faucets is, that a portion of the precipitated gold lodges in the bore, and it is necessary, on opening the faucet, to place a bucket under it to receive the first liquid which flows. Faucets often give trouble by leaking, especially when used for metallic solutions, which have a tendency to cause wood to shrink. Plugs are also objectionable on account of their liability to leak. If used they must fit flush with the inside of the tub.
A piece of rubber hose, applied as a syphon, answers very well, if prevented from drawing too near the bot torn of the vat, by fastening a strip of wood to it so that the wood projects beyond the end of the hose. A better plan is, to insert in each end of the hose a tightly fitting piece of lead pipe, which is coiled once round in a spiral form. The hose having been filled with water, is laid across the side of the vat, the inner end dipping beneath the surface of the liquid.
Air cannot pass the curves in the leaden portion of the syphon while it is full of liquid, so that if the workman neglects to lower it as the liquid in the vat subsides, no inconvenience results, and the flow is resumed as soon as the inner end is lowered by drawing the hose over the side of the vat.