PROOFS OF THE PROPERTIES OF GOLD.

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Remark. ...Though nitro-muriatic, or more properly oxige-uated muriatic acid, is the only fluid capable of dissolving gold,it has been long ago noticed that nitrous acid, assisted by heat,exercised some slight action on this metal, especially when in astate of extreme comminution.

Experiment II.

Gold is precipitated from its solution ly tin.

CPreparation of the purple precipitate of Cassius.)

If we immerse into a solution of gold in nitro-muriatic acid asheet of tin, the oxid of gold is precipitated of a purple colour,and, when scraped off and collected, forms the purple pow-der, or precipitate of Cassius, much employed in enamelling.It is a compound, consisting of oxid of gold and oxid of tin.It is best obtained, for the purpose of enamelling, by dissolvingpure tin in diluted nitro-muriatic acid, composed of two parts ofnitric and one of muriatic acid, very slowly, and absolutely with-out heat, and then adding to this fresh-prepared solution, dilutedwith at least eighty times its weight of distilled water, a solutionof pure gold in nitro-muriatic acid, collecting the precipitate,and washing it repeatedly with distilled water.

Rem ark... It is absolutely necessary that the tin should beoxidated at its minimum, for the oxi-muriate of tin, which isalready at a maximum of oxidation produces no such effect, be-cause it cannot abstract oxigen from the oxid of gold.

Experiment III.

Gold is precipitated from its solution ly charcoal.

Into a perfectly neutral diluted solution of gold, contained ina glass jar, put a long narrow slip of well-burnt charcoal, and

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