Potassium dicyanidoaurate (I)
Structural formula | |||||||||||||||||||
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General | |||||||||||||||||||
Surname | Potassium dicyanidoaurate (I) | ||||||||||||||||||
other names |
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Molecular formula | K [Au (CN) 2 ] | ||||||||||||||||||
Brief description |
colorless, odorless solid |
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properties | |||||||||||||||||||
Molar mass | 288.10 g mol −1 | ||||||||||||||||||
Physical state |
firmly |
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density |
3.45 g cm −3 |
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solubility |
soluble in water |
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safety instructions | |||||||||||||||||||
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As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . |
Kaliumdicyanidoaurat (I) , K [Au (CN) 2 ], is a potassium - salt of the complex Dicyanidoaurat (I) - anions [Au (CN) 2 ] - . The gold content of the salt is around 68.2%. The complex is 100 times more stable than yellow blood liquor salt .
As a result of this complexation, the gold ion concentration in water drops so extremely that it reduces the normal potential of gold (+1.69 volts) to the potential of a base metal (+0.20 volts). Therefore, in cyanide leaching, elemental gold is oxidized with atmospheric oxygen.
Cyanide leaching
When gold is extracted ( cyanide leaching ), solutions of potassium dicyanidoaurate (I) are formed:
To isolate the gold in elemental form, this complex is then reduced with zinc (Zn):
use
The connection is used in electroplating for gold-plating conductive materials. During electrolysis , these are switched as a minus pole. In this cathode region, the [Au (CN) are 2 ] - - anion is reduced to a thin layer of gold.
Individual evidence
- ↑ a b c Entry on potassium dicyanoaurate (I) in the GESTIS substance database of the IFA , accessed on January 8, 2018(JavaScript required) .
- ↑ a b data sheet potassium gold cyanide from AlfaAesar, accessed on January 22, 2018 ( PDF )(JavaScript required) .
- ↑ Not explicitly listed in Regulation (EC) No. 1272/2008 (CLP) , but with the indicated labeling it falls under the group entry salts of hydrogen cyanide with the exception of complex cyanides such as ferrocyanides, ferricyanides and mercuric oxycyanide and those specified elsewhere in this Annex in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
- ↑ chemieunterricht.de: Applications of complexation , see also Nernst equation
- ^ AG Gray, HW Dettner: Modern galvanic metal deposition , Carl Hanser, Munich. doi : 10.1002 / bbpc.19590630528 .