Potassium aurocyanide

A further series of five experiments was made to determine the ratio of the electrochemical equivalents of gold and silver, by passing the same quantity of electricity through solutions of potassium aurocyanide,... 

Aurous sulphide, Au2S.—The pure sulphide can be prepared7 by saturation of a solution of potassium aurocyanide with hydrogen sulphide, and precipitation of the salt by acidifying the solution with hydrochloric acid. It is not produced by the action of hydrogen sulphide on a hot solution of auric chloride, as supposed by Berzelius.8 The moist substance has- a steel-grey colour when dried, it becomes brownish black. When freshly prepared, the sulphide dissolves in water to a colloidal solution, from which it is reprecipitated by addition of hydrochloric acid. The sulphide is unaffected by dilute acids, but is decomposed by powerful oxidizers such as aqua regia and chlorine. It is readily dissolved by solutions of polysulphides,0 and less readily by those of monosulphides. It also dissolves in a solution of potassium... 

Double decomposition of ammonium sulphate and potassium aurocyanide yields ammonium aurocyanide, NH4Au(CN)2. This substance begins to decompose at 100° C. into aurous cyanide, hydrogen cyanide, and ammonia.7 Sodium aurocyanide, NaAu(CN)2, resembles the corresponding potassium salt in both preparation and properties. Salts of the aurocyanic radical, Au(CN)2, with other metals are also known.8 The compound HAu(CN)2 has not been isolated, since it decomposes readily with production of hydrogen cyanide. 

The gold thns passes into solution as potassium aurocyanide, KAu(CN)2. 

Chloroauric acid (HAuCD) or auric chloride (AuCD or AU2CI6) is usually used but complex salts, such as potassium aurocyanide (KAu(CN)2) and the ethylenediamine complex [Au(en)2]Cl3, are alternatives. Traditional supports are silica, alumina and magnesia, but titania, alumina, boehmite (AIO(OH)), ferric oxide (a-Fe203) and magnesium hydroxide can also be used [18]. 

Synonyms potassium dicyanoaurate (I) potassium cyanoaurite gold (I) potassium cyanide potassium aurocyanide bis(cyano-C)-aurate(i-) potassium potassium cyanoaurate (I)... 

Cyan-essigsaure, /. cyanoacetic acid, -gas, n. cyanogen gas. -gold, n. gold cyanide, -gold-kalium, n. potassium auri- or aurocyanide, potassium cyanoaurate. 

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