โ Scribed by C.W. Davis
No coin nor oath required. For personal study only.
BECAUSE of the extensive use o~ platinum and white gold in jewelry, the Bureau of Mines has received numerous inquiries concerning the recovery of the valuable metals from scrap, filings, sweeps, and other waste. Although persons who have had only a little laboratory experience can use some of the methods, the separation and recovery of the platinum metals is intricate and should be performed only by a skilled chemist. For this reason it is advisable either to employ such a chemist or to ship the material to one of the many refiners of platinum.
Platinum, gold, and silver, and alloys containing two or more of the metals mentioned here--platinum, iridium, gold, palladium, silver, copper, nickel, zinc, and manganese--are likely to be present in material from which the jeweler wishes to recover the valuable metals. Certain mixtures of these metals and alloys may be treated more easily than others; consequently the methods for the recovery of the metals are separated into classes. Where group separations, only are required, any or all of the valuable metals may be present either free or alloyed, except that if alloyed the aIIoy or alloys containing one or more of the metals platinum, iridium, and palladium must be free from gold, silver, or appreciable amounts of copper and zinc; and the alloy or alloys containing gold, silver, and base metals must be free from platinum, iridium, and palladium. The separation will recover platinum, iridium, and palladium in one group, and gold, silver, and base metals in another group. This method depends on the fact that gold, silver, and base metals alloy directly with mercury to form amalgams, but the other metals form an alloy only under certain conditions, such as in the presence of zinc amalgam, acid, and copper sulphate. Zinc or tin must be absent, as an amalgam would be formed with them and the platinum-group metals would go with the amalgam. * Communicated by the Director.
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