PROOFS OF THE PROPERTIES OF GOLD. 1 67

means of a camel-hair pencil, the gold may be so applied as toexhibit regular ornaments, or figures, when reduced.

The same reduction takes place when the silk is dipped intophosphorated ether. If a piece of silk, moistened with phospho-rated ether, be immersed in the nitro-muriatic solution, its sur-face is immediately gilt with a fine coat of gold, which adheresvery strongly.

That phosphorated hidrogen gas produces the same effect hasbeen noticed already, (vol. i. p. 276). Sulphureous acid gas hasa similar effect.

Remark. ..Mrs. Fulhame has proved* that the presence ofmoisture is absolutely necessary for the reduction of gold. It isdifficult to ascertain what makes water so indispensably neces-sary. It is not, as might be, supposed, requisite to secure thefluidity of the mixture; for she has ascertained that sulphuricether, though a fluid, does not answer, except water be pre-sent. She accounts very ingeniously for the phenomena, bysupposing the water to be decomposed. The combustible com-bines with its oxigen, while its hidrogen unites to the oxigen ofthe gold, and re-produces water. This theory accounts very wellfor the phenomena; but it would require some direct proofs toestablish it completely.

Experiment VI.

Decomposition of nitro-muriate of gold by ammonia.

(Preparation of fulminating gold.)

Dissolve pure gold in nitro-muriatic acid to saturation, anddilute the solution with three times its bulk of distilled water,and add to it gradually some pure ammonia, a yellow precipitate

L 4

In her Essay on Combustion.