A supplement to Ures Dictionary of Arts, Manufactures, and Mines, : containing a clear exposition of their principles and practice. . , which, not being fusible, is capable of being stiiicd up with thefused mass of gold, just as sand may be stirred up with mercury, but witli this groat advan-tage, that the oxide of copper contains oxygen, with which it parts readily to oxidize anymetal having a greater affinity for oxygen than itself The metals, once oxidized, becomelighter than the fused metal, and mixing mechanically, or combining chemically with theblack oxide of copper, float to the surfac
A supplement to Ures Dictionary of Arts, Manufactures, and Mines, : containing a clear exposition of their principles and practice. . , which, not being fusible, is capable of being stiiicd up with thefused mass of gold, just as sand may be stirred up with mercury, but witli this groat advan-tage, that the oxide of copper contains oxygen, with which it parts readily to oxidize anymetal having a greater affinity for oxygen than itself The metals, once oxidized, becomelighter than the fused metal, and mixing mechanically, or combining chemically with theblack oxide of copper, float to the surface and are removed. In the execution of proposition, it is imperative to use crucibles free from reducing agents, suchas carbon, and it is found that half an hour is sufficient time to allow the contact of theoxide of copper with the fused gold. It has been generally stated by those supposed to be acquainted with the subject, thatgold containing tin, antimony, and arsenic is so brittle as to render it wholly unfit for coin-ing. Tills requires modification, for although these metals, as well as lead, render gold so. REFINING GOLD AND SILVER. 947 brittle that it will readily break between tlie fingers, yet it is not true to say that it rendersgold so brittle as to be incapable of being coined. In June and Jnly, 1859, some brittlegold, to the extent of about 04,000 ounces, passed through the Mint. The bars were sobrittle that they broke with the slighest blow from a hammer, but by special treatment thegold was coined into the toughest coins ever produced. It may now be stated that if thesystem of manufacture be changed to suit the recjuirements of the case, gold cannot befound too brittle for the purpose of coining. This is simply a matter of fact, but the ex-pense of coining brittle gold is undoubtedly very great; it is thereibre wise that Mr. War-ringtons plan should be adopted for all gold containing the volatile metals or tin. Osniium-iridium does not render gold
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