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°.
It begins to decompose into gold and chlorine at 185°, the decomposition being complete at 230°; water decomposes it into gold and auric chloride.
Auric chloride, or gold trichloride, AuC1 3, is a dark rubyred or reddish-brown, crystalline, deliquescent powder obtained by dissolving the metal in aqua regia.
The potassium salt is obtained by crystallizing equivalent quantities of potassium and auric chlorides.
Auric chloride combines with the hydrochlorides of many organic bases - amines, alkaloids, &c. - to form characteristic compounds.
Water decomposes it into gold and auric chloride.
Aurous bromide, AuBr, is a yellowish-green powder obtained by heating the tribromide to 140°; auric bromide, AuBr 3, forms reddish-black or scarlet-red leafy crystals, which dissolve in water to form a reddishbrown solution,and combines with bromides to form bromaurates corresponding to the chloraurates.
Aurous iodide, Aul, is a light-yellow, sparingly soluble powder obtained, together with free iodine, by adding potassium iodide to auric chloride; auric iodide, Au13, is formed as a dark-green powder at the same time, but it readily decomposes to aurous iodide and iodine.
Auric cyanide, Au(CN) 3, is not certainly known; its double salts, however, have been frequently described.
Potassium auricyanide, 2KAu(CN) 4.3H 2 O, is obtained as large, colourless, efflorescent tablets by crystallizing concentrated solutions of auric chloride and potassium cyanide.
Auric sulphide, Au 2 S 31 is an amorphous powder formed when lithium aurichloride is treated with dry sulphuretted hydrogen at - 10°.
Sodium aurothiosulphate, 3Na 2 S 2 O 3 Au2S203.4H20, forms colourless needles; it is obtained in the direct action of sodium thiosulphateongoldinthe presence of an oxidizing agent, or by the addition of a dilute solution of auric chloride to a sodium thiosulphate solution.
It forms addition compounds with mercuric and auric chlorides.
They form characteristic compounds with mercuric and auric chlorides.
This oxide is slightly basic. Auric oxide, Au203, is a brown powder, decomposed into its elements when heated to about 250° or on exposure to light.
The auric chloride is, however, decomposed at the elevated temperature into finely divided metallic gold, which is then readily attacked by the chlorine gas.