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发表于 2011-9-15 00:44:36
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本帖最后由 Highway 于 2011-9-15 00:47 编辑
锦候 发表于 2011-9-14 13:53 
不是我故意败你的兴致，不过我了解的情况真的不是这样的。
这些是约定成俗的说法，就像2 by 4不是真的2英 ...
你那位朋友的知识曾经是对的，但是需要更新了。
工业界大概在40年前就可以生产9999纯度的黄金了，美国业界大概是1982年成熟的，加拿大看来要早几年。除了中国，世界上主要的金币生产国都是9999纯度的黄金了（南非的格鲁巴和美国的鹰币例外，是22K金）。
这里有篇文章，你可以看看。如果有兴趣的话，不妨转给那位朋友，让他也更新一下知识。
Refining Gold Explained!
The process of refining gold is necessary to obtain gold of the greatest possible purity from a myriad of sources. These may include industrial scrap, recycling banks, primary producers of precious metals, dealers, financial institutions, and mints. The mechanical preparation and concentration of ore is termed ore dressing; it produces gold that is often an admixture with trace impurities and some silver. Further treatment is necessary to remove the contaminants in freeing and refining gold.
Refining gold may be done by any of several methods, all quite technologically advanced. Huge amounts of refined gold are produced by some of the biggest refineries in the United States: the capacity to produce more than 10 million troy ounces each year is not unusual. During the past 40 years or so, the standard methods of refining gold were able to produce gold that was .9999 fine. In 1982, bullion coins of .9999 purity were produced by the best American refineries. Today one can buy the first American solid gold 24K bullion coin, the American Buffalo $50 coin. On the obverse (heads) side is shown the profile of a Native American chief, and on the reverse (tails) side, a picture of the buffalo. The weight, content, and purity of this .9999 fine coin are guaranteed by the US government. The coin sells for $918.77! The most highly-developed technological processes of the present day for refining gold yield a gold that is .99999 pure, to be used for granulation – a technique of jewelry embellishment that solders tiny spherical droplets of gold onto a base.
These are the two stages of the process of refining gold:
• The feed material of gold ore is treated with the Miller chlorination process, a pyrometallurgical operation in which the gold is heated in crucibles until melted, then exposed to chlorine gas. Although chlorine does not react with gold, it does combine with silver and other impurities in the ore to form chlorides. These float to the surface and can be skimmed off to leave behind gold that is .995 pure and therefore meets the requirements of the London bullion market.
• Some end-use customers require gold that is even more pure. The .995 pure gold is cast into anodes. These are placed in an electrolyte solution, along with cathodes of pure gold. When an electric current passes from anode to cathode through the electrolyte solution, the anodes dissolve, and the pure gold in them passes to the cathodes. It is a long process of refining gold, requiring about two days, but it does produce gold that is .99999 pure. At the end of the operation, the gold-coated cathodes are removed, molten, and cast into bars.
Another process for refining gold treats it with sulphuric, nitric, and hydrochloric acids. These do not react with gold, but do react with impurities. In the final stage of this process, the purified gold is molten and cast into bars weighing approximately 28 pounds.
Still another way of refining gold is the fire assay process, using the technique of cupellation. This is an old technique that was used to separate silver or gold from lead or other base metals. Essentially, an alloy of gold and other metals, including lead, is melted at a high temperature and then allowed to freeze. When it is cooled, a small amount of precious metal (gold and silver) and lead remains, and a slag is formed of base metals and other impurities. The “button” of gold and silver is again subjected to extremely high heat; the lead oxidizes and goes into the atmosphere. Finally, the small piece of gold and silver is placed in nitric acid, which dissolves the silver and leaves the 24K pure gold. This ancient method of refining gold should only be used for small quantities of gold, not more than 10 grams, because the process emits large quantities of highly toxic lead oxide fumes.
For refining gold in larger quantities, a more ecologically-sound technique can be used; for example, inquartation and parting. This involves melting the gold to be refined in an alloy with silver or copper, such that the gold makes up about 25 percent of the alloy. The base metal is then dissolved in acid, preferably nitric acid, which removes all but the gold. The resulting gold sludge may be treated with a secondary bath of hydrochloric acid, and is then washed and drained. Inquartation and parting has been found to be useful in treating gold scrap of 10K to 14K; the necessary additions of silver or copper may already be present in the scrap material. It should be noted that these last three processes for refining gold must only be performed in an appropriately specialized industrial environment.
On a very much smaller scale, refining gold at home is even possible. Chemical kits requiring a minimum of equipment are available; usually you only need a battery charger with DC current and a few Pyrex glass vessels. Such kits purport to be completely safe, and are sold as science experiments for older children. Look on the Internet to find more details about suppliers.
国外铸币，尤其是那种有Face Value的国币都是按照法律条纹来生产的。譬如美国的鹰币就是国会通过了Gold Bullion Coin Act of 1985以后才依法铸造的，美国政府要保证它的品质的。加拿大的枫叶币是根据Canadian Currency Act and the Royal Canadian Mint Act两项法令来铸造的。这和和小贩产果汁是两码事儿。 |
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发表于 2011-9-14 11:58:26
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