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how is a stamp mill to recover gold

Mercury and free gold can be brought together in a number of ways, but to mix well, both the mercury and gold must be clean. Coatings, especially those which are oily in nature, prevent the two from mixing. In the old days, miners placed mercury in the riffles of sluices, dry washers, and similar devices to aid capture of fine gold. At the base of most of the old stamp mills was a plate amalgamator – a device with a metal plate coated with a thin film of mercury on the surface. Crushed ore or concentrates was fed slowly over the plate, and gold adhered to the mercury. Using “open system” methods like these where any mercury lost through the system went out with the tailings into the environment would be crazy today, and simply an invitation for a big dollar citation from every environmental agency that has jurisdiction over you. Learn More

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amalgamation: using mercury to capture finegold, retort

The greatest potential disadvantage of amalgamation is the health hazard presented by mercury. Mercury is toxic. It attacks your nervous system doing damage over a long period time. It has the characteristic of not being easily excreted from the body, so if you feel fine, it still may affect you in the long term. If you ingest a large amount of Mercury for example, it will stay in your body for a long time. On the other hand, if you ingest only a little Mercury each day it will accumulate in your body until, if you take no action, it can eventually produce toxic symptoms such as hair loss etc. The term “Mad Hatter”, or “mad as a Hatter” derives from the very real situation that hat makers in the 18th century used Mercury to process felt, a commonly used hat making material of that time. After years of being in the business, exposure to small amounts of mercury vapor each day quite literally made them insane. It's certainly not the type of situation which you would like to also inflict upon yourself.

Mercury has a relatively high vapor pressure, which means that at normal temperatures if you left a bowl of mercury out in the air a significant amount would vaporize and would evaporate to the air. If you continued to breathe this Mercury containing air you certainly would ingest a significant amount of Mercury. The most dangerous thing about Mercury is that the lungs will readily absorb the vapors. While Mercury is only slowly absorbed through the skin is still worthwhile to protect yourself. Even though Mercury was once used in various forms for medical purposes, most of these uses have now been banned for health reasons

"Clean" Mercury can mean different things to different people. It most commonly means that it is clean enough that clean gold touching it will be amalgamated. There are a number of ways to clean Mercury, perhaps the easiest is to squeeze it through a wet chamois. Clean Mercury will pass through the chamois and come out as tiny droplets.  This process will filter out any junk and most oils that contaminated the Mercury, and the process is fairly quick. Unless your Mercury was extremely oily, it should now be clean enough to use in amalgamation

amalgamation: using mercury to capture finegold, retort

A recent innovation in the use of mercury in treating concentrates is to charge it by introducing a small amount of a very active metal like sodium or potassium. The resulting product is called "charged mercury" and will amalgamate with gold in an aggressive manner.  In many situations where the gold might not amalgamate because it was just slightly coated, the charged Mercury will attack it through the coating and successfully amalgamate.  "Charged mercury" is nothing magical it is really not that difficult to make.  You could just take some sodium metal and drop little chunks of it into liquid mercury, but that is dangerous and sodium metal is also dangerous and hard to acquire.  

Charging mercury is such a simple procedure that it is amazing that so few prospectors know how to do it. In order to charge Mercury, you must first make concentrated solution of sodium chloride (salt) and turn your Mercury into an electrolytic cell.  Mercury is poured into the bottom of a container and the salt solution is poured on top of the mercury. You should have a least a few inches of salt solution over the top of the mercury.  An insulated heavy copper wire is put down into the mercury, and the insulation should go right into the mercury, so the copper is not exposed to the salt solution. A graphite rod is stuck into the solution but not touching the mercury - a good gap between them needs to be maintained.  DC current from a supply such as a battery charger (turn it down to 6 V) is applied to both the mercury and the graphite rod. Polarity is important, so be sure to hook the plus and minus to the right contacts. The plus side should be attached to the carbon rod, and the minus to the wire. When you done it right, Chlorine gas bubbles off the graphite rod, and sodium goes into the mercury.  This is actually a dangerous process, because chlorine is quite toxic in its own right (chlorine is outlawed under the Geneva Convention as a weapon). Chlorine gas can kill you quickly, so be very careful and don't breathe it.  This is actually a miniature version of the industrial process used around the world to make chlorine gas, chlorine bleach (like we use in our washing machines) and lye. Eventually the mercury will become hardened, after which it is now fully charged and the voltage can be shut off, and the charged Mercury used. This process must be done outdoors, and you should not attempt this procedure unless you have a full understanding of the chemistry and safety hazards involved. If you don't understand the hazards and don't want to learn them, just use your Mercury and an uncharged state. Mercury is best stored in an uncharged state and then charged and used as needed. To be honest, I do not charge my mercury

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