Gold potassium cyanide

With gold, potassium cyanide forms complex derivatives, and it is employed in the extraction of the metal (p. 324). As a double cyanide with other metallic cyanides, such as those of silver, gold, and nickel, it is an important reagent in electroplating. It is also employed in photography. Like hydrocyanic acid, it is extremely poisonous. 

Gold potassium cyanide. See Potassium gold cyanide... 

Potassium gold cyanide CAS 13967-50-5 EINECS/ELINCS 237-748-4 Synonyms Aurate(l-), bis (cyano-C), potassium Aurate(l-), dicyano-, potassium Bis (cyano-C) aurate(l-) potassium Gold potassium cyanide Monopotassium dicyanoaurate Potassium dicyanoaurate Potassium dicyanoaurate (I)... 

Stoddard solvent 1,1,2,2-Tetrachloroethane extraction, fish protein 2-Butanol extraction, gold Potassium cyanide... 

Gold potassium cyanide (purplish-brown discoloration, onycholysis) in electroplaters, electronic workers (Budden and Wilkinson 1978)... 

Budden MG, Wilkinson DS (1978) Skin and nail lesions from gold potassium cyanide. Contact Dermatitis 4 172-173 Buendia-Eisman A, Serrano-Ortegas, Ortega del Olmo RM (1997) Hair fragments as a subungual foreign body. Eur J Dermatol... 

In the presence of air, it is attacked by potassium cyanide solution, to give the complex dicyanoaurate(I) ion, in which gold has an oxidation state + 1 ... 

Cyanides. Salts of the complex ion, [Au(CN)2] , can be formed directiy from gold, ie, gold dissolves ia dilute solutions of potassium cyanide ia the presence of air. Additionally, a gold anode dissolves ia a solution of potassium cyanide. The potassium salt can be isolated by evaporation of the solution and purified by recrystallization from water (177). Boiling of the complex cyanide ia hydrochloric acid results ia formation of AuCN [506-65-01]. Halogens add oxidatively to [Au(CN)2] to yield salts of [Au(CN)2X2] which are converted to the tetracyanoaurates usiag excess cyanide (178). These last can also be prepared directiy from the tetrahaloaurates. 

Sodium cyanide [143-33-9] NaCN, is a white cubic crystalline soHd commonly called white cyanide. It was first prepared in 1834 by heating Pmssian blue, a mixture of cyanogen compounds of iron, and sodium carbonate and extracting sodium cyanide from the cooled mixture using alcohol. Sodium cyanide remained a laboratory curiosity until 1887, when a process was patented for the extraction of gold and silver from ores by means of a dilute solution of cyanide (see Metallurgy, extractive). A mixture of sodium and potassium cyanides, produced by Edenmeyer s improvement of the Rodgers process, was marketed in 1890. 

Potassium cyanide [151 -50-8] KCN, a white crystalline, deUquescent soHd, was initially used as a flux, andlater for electroplating, which is the single greatest use in the 1990s. The demand for potassium cyanide was met by the ferrocyanide process until the latter part of the nineteenth century, when the extraordinary demands of the gold mining industry for alkah cyanide resulted in the development of direct synthesis processes. When cheaper sodium cyanide became available, potassium cyanide was displaced in many uses. With the decline in the use of alkah cyanides for plating the demand for potassium cyanide continues to decline. The total world production in 1990 was estimated at about 4500 t, down from 7300 t in 1976. 

Potassium cyanide is primarily used for fine silver plating but is also used for dyes and specialty products (see Electroplating). Electrolytic refining of platinum is carried out in fused potassium cyanide baths, in which a separation from silver is effected. Potassium cyanide is also a component of the electrolyte for the analytical separation of gold, silver, and copper from platinum. It is used with sodium cyanide for nitriding steel and also in mixtures for metal coloring by chemical or electrolytic processes. 

The reaction is a sensitive one, but is subject to a number of interferences. The solution must be free from large amounts of lead, thallium (I), copper, tin, arsenic, antimony, gold, silver, platinum, and palladium, and from elements in sufficient quantity to colour the solution, e.g. nickel. Metals giving insoluble iodides must be absent, or present in amounts not yielding a precipitate. Substances which liberate iodine from potassium iodide interfere, for example iron(III) the latter should be reduced with sulphurous acid and the excess of gas boiled off, or by a 30 per cent solution of hypophosphorous acid. Chloride ion reduces the intensity of the bismuth colour. Separation of bismuth from copper can be effected by extraction of the bismuth as dithizonate by treatment in ammoniacal potassium cyanide solution with a 0.1 per cent solution of dithizone in chloroform if lead is present, shaking of the chloroform solution of lead and bismuth dithizonates with a buffer solution of pH 3.4 results in the lead alone passing into the aqueous phase. The bismuth complex is soluble in a pentan-l-ol-ethyl acetate mixture, and this fact can be utilised for the determination in the presence of coloured ions, such as nickel, cobalt, chromium, and uranium. 

Potassium cyanide is a salt that dissociates completely into ions, and the problem states that gold... 

Potassium cyanide 151-50-8 Extraction of gold and silver from ores Pesticide Fumigant Electroplating... 

Potassium cyanide (KCN) is a white crystalline substance with a slight odor of bitter almonds. It is produced when hydrogen cyanide is absorbed in potassium hydroxide. It is used to extract gold and silver from their ores, in electroplating computer boards, and as an insecticide. Potassium cyanide is very toxic to the skin or when ingested or inhaled, and it is used as a source of cyanide (CN) gas in gas chambers. 

The complex cyanide, Na[Au(CN)2] is made by dissolving gold in a dilute solution of sodium cyanide in the presence of air or by dissolution of a gold anode in a solution of sodium cyanide during electrolysis. The solution is evaporated to separate the complex, Na[Au(CN)2], which is purified by recrystallization from water. Potassium cyanide may be used instead of sodium cyanide to prepare gold(I) cyanide. 

Brown powder decomposes slowly on exposure to sunhght or by heating at 150°C begins to release oxygen at 110°C fuUy decomposes to metallic gold at 250°C insoluble in water soluble in hydrochloric and concentrated nitric acids also soluble in aqueous solutions of sodium- or potassium cyanide. 

Potassium cyanide is used in extracting gold, silver and platinum from... 

Cyanide. Sodium cyanide. [CAS 143-33-9]. NaCN. white solid, soluble, very poisonous, formed (1) by reaction of sodamide and carbon at high temperature, (2) by reaction of calcium cyanamide and sodium chloride at high temperature, reacts in dilute solution in air with gold or silver to form soluble sodium gold or silver cyanide, and used for this purpose in the cyanide process for recovery of gold. The perceniage of available cyanide is greater than in potassium cyanide previously used. Used as a source of cyanide, and for hydrocyanic acid. 

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