Gold, Fulminating.
This is a yellowish-brown substance, precipitated on adding ammonia to a strong solution of chloride of gold.
It may be dried carefully at 212°, but explodes violently on being heated suddenly about to 290°. Friction also causes it to explode when dry; but the moist powder may be rubbed or handled without danger. It is decomposed by sulphuretted hydrogen.
Fulminating gold is probably an aurate of ammonia, containing 2 atoms of ammonia to 1 atom of peroxide of gold.
Symbol, AuO S{2}O{2}. Atomic Weight, 253.
Hyposulphite of gold is produced by the reaction of chloride of gold upon hyposulphite of soda.
The salt sold in commerce as sel d'or is a double hyposulphite of gold and soda, containing one atom of the former salt to three of the latter, with four atoms of water of crystallization. It is formed by adding one part of chloride of gold, in solution, to three parts of hyposulphite of soda, and precipitating the resulting salt by alcohol; the chloride of gold must be added to the hyposulphite of soda, and not the soda salt to the gold.
Properties.—Hyposulphite of gold is unstable and cannot exist in an isolated state, quickly passing into sulphur, sulphuric acid, and metallic gold. When combined with excess of hyposulphite of soda in the form of sel d'or, it is more permanent.