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.
The potassium salt is obtained by crystallizing equivalent quantities of potassium and auric chlorides.
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.
They are soluble in water and give characteristic precipitates with platinic and auric chlorides, and with potassium ferrocyanide.
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.
The auric chloride is, however, decomposed at the elevated temperature into finely divided metallic gold, which is then readily attacked by the chlorine gas.
They form characteristic compounds with mercuric and auric chlorides.
Water decomposes it into gold and auric chloride.
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.