ANALYSIS OF ORES OF GOLD.

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gold in its metallic state. The presence of copper in the oremay be detected by immersing a plate of iron in the solution,which will become coppered. Iron may be detected by tinctureof galls, which occasions a blackish precipitate ; and platina, bymuriate of ammonia, which separates it. The minutest quantityof gold contained in an ore may be investigated, by letting fallinto the solution a few drops of a solution of tin in muriatic acid,and which will instantly cause a purple precipitate.

When gold is found in sands it can be obtained by simplywashing the sand, for the lighter foreign substances will remainlonger suspended, and carried off with the water, while theheavy particles of gold sink to the bottom with greater celerity.

PARTING, or QUARTATION.

If gold be alloyed with silver, it is purified by a process some-times called parting, and sometimes quartation : this last nameis given on account of the proportion of materials employed;three parts of silver being added to the alloy, which of coursemakes a fourth part of the mixture. They are melted together,and sulphur thrown in: the. sulphur combines with the silver,and the gold falls to the bottom. In the humid way gold is pu-rified from silver by the nitric acid, which rapidly dissolves silver,but has no action upon gold.

CUPELLATION.

If gold be alloyed with copper, lead, &c. it is purified by theprocess called cupellation, in the following manner: the alloyedgold is put with<about twice its weight of silver, and some lead,into a crucible made of a very porous substance, such as bone-ashes, and called a cupel. They are all exposed to a considerableheat, which oxidates the lead, or converts it into a semi-vitreous