They are soluble in water and give characteristic precipitates with platinic and auric chlorides, and with potassium ferrocyanide.
Aurous oxide, Au 2 0, is obtained by cautiously adding potash to a solution of aurous bromide, or by boiling mixed solutions of auric chloride and mercurous nitrate.
When a concentrated solution of auric chloride is treated with caustic potash, a brown precipitate of auric hydrate, Au(OH) 3, is obtained, which, on heating, loses water to form auryl hydrate, AuO(OH), and auric oxide, Au 2 0 3.
With concentrated ammonia auric oxide forms a black, highly explosive compound of the composition AuN2H3.3H20, named " fulminating gold "; this substance is generally considered to be Au(NH 2)NH.
Aurous chloride, AuCl, is obtained as a lemon-yellow, amorphous powder, insoluble in water, by heating auric chloride to 185°.