THE USE OF THE BLOW PIPE.

Otago Witness, Issue 1813, 20 August 1886, Page 36

THE USE OF THE BLOW PIPE.

GOLD CContimied}. What was said in my last article may be thus summarised: Native gold usually con- • tains silver, and can easily be recognised if the silver does not exceed 30 per cent. When more than 30 per cent, of silver is present, the gold may be detected by the treatment with nitric acid. The acid must be slightly diluted —three or four parts of acid to one of water. Before submitting the bead to the action of the acid it had better be flattened, and if. a watch glass or small porcelain capsule cannot be obtained, little china toy cups will answer admirably. Those holding nearly a teaspoonful will be the best size. They can be bought at any toy shop for about a shilling a set. Of course nitric acid must not be put into metal vessels, such as spoons, &c. for it has the property of dissolving most metals very violently. Gold is also found in a mineral of a steelgrey colour, called Sylvanite, which is a compound containing about 28 per cent. of. gold and 15 per cent, of silver, the rest being a volatile substance called tellurium. By fusing on charcoal in either flame, the tellurium is driven off and an alloy of gold and silver left. (I have not performed this experiment.) Gold amalgam is a heavy grey mineral, which, when fused on charcoal, yields a globule of gold more or less pure.