"Stop a moment," said the Bishop. The team was halted. "My good man," said the Bishop, addressing the wood-sawyer, "put on your hat. The sun will bake your brain."
The man looked up in surprise, and then a look of disgust came over his face.
"D'you s'pose," said he, "that 'f I had any brains I'd be sawing wood in this land of silver?"
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SEPARATING GOLD FROM ALLOY.
Gold coins and gold jewelry always contain alloy. Gold being too soft a metal to use alone is mixed with some harder metal, so that the article will wear longer. Pure gold is 24 carats fine. Before the metric system was adopted, a mark—a gold coin—was used as the unit of standard weight, and a carat is 1/24 of the weight of a mark. A carat is used to express the proportion of gold in the alloy. If a coin is 22 carats fine, it means that it contains 22 parts of pure gold. An article that is 18 carats fine contains 18 parts of pure gold and 6 parts of alloy. Gold coins contain so little alloy that it is not necessary to separate the gold from the alloy; but if one is preparing chloride of gold from old jewelry, in which are found perhaps only nine parts of pure gold, it is best in using it for special work to separate the two metals. This can be done with very little trouble.
Dissolve the gold in "aqua-regia," according to the directions given in the last number of the Round Table. When it is dissolved and the acid evaporated, dilute the chloride with clear water, and add a small quantity of ferrous sulphate. This will cause the gold to be precipitated, and it will settle to the bottom of the vessel in the form of a brown powder, while the alloy will remain in solution. It will take some time for the gold to settle, and when it is all deposited or precipitated turn off the water carefully, wash the gold in distilled water, and then redissolve it in fresh aqua-regia, following the directions in our last paper on preparing chloride of gold. Ferrous sulphate, the substance which precipitates the gold, is also called sulphate of iron. It is a chemical compound, and the chemical formula is FeSO4+7H2O, meaning that one atom of iron, one of sulphur, and four of oxygen are added (+) to 7 molecules of water (7H2O).