Tetrachloroauric acid

Structural formula
General
Surname	Tetrachloroauric acid
other names	Chloroauric acid; Hydrogen tetrachloroaurate (III); Tetrachloroauric acid;
Molecular formula	H [AuCl 4 ]
Brief description	lemon yellow needles
External identifiers / databases
EC number	240-948-4
ECHA InfoCard	100.037.211
PubChem	28133
Wikidata	Q411357
properties
Molar mass	339.786 g mol −1
Physical state	firmly
density	3.9 g cm −3 (trihydrate)
Melting point	approx. 30 ° C (trihydrate)
solubility	easily in water (150 g l −1 at 20 ° C, trihydrate)
safety instructions
H and P phrases	H: 314-317
	P: 280-301 + 330 + 331-302 + 352-305 + 351 + 338-308 + 310
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Tetrachloroauric acid , HAuCl ₄ is a chemical compound of gold and chlorine and an important starting material for other gold compounds.

Extraction and presentation

The simplest and most important way of obtaining tetrachloroauric acid is the dissolution of elemental gold in aqua regia , a mixture of hydrochloric and nitric acid . Nitrosyl chloride - the active reagent in aqua regia - has to be removed by smoking with hydrochloric acid, which releases nitrous gases or nitrogen dioxide :

{\ displaystyle \ mathrm {2 \ Au + 2 \ NOCl + 3 \ Cl_ {2} +2 \ HNO_ {3} \ rightarrow}}

{\ displaystyle \ mathrm {2 \ HAuCl_ {4} +4 \ NO_ {2}}}

Another way of producing tetrachloroauric acid is the reaction of gold (III) chloride and hydrochloric acid.

{\ displaystyle \ mathrm {AuCl_ {3} + HCl \ longrightarrow HAuCl_ {4}}}

properties

Tetrachloroauric acid, crystalline

Tetrachloroauric acid crystallizes in long, pale yellow needles that dissolve easily in a moist environment . It dissolves easily in water and ethanol . It has a monoclinic crystal structure with the space group P 2 ₁ / c (space group no. 14) (a = 6.57, b = 11.6, c = 15.0 Å , β = 104 °). Template: room group / 14

use

Since tetrachloroauric acid is easy to obtain, it is used as a starting material for the production of other gold compounds. In photography it is used for clay baths to give the photo a purple hue. Tetrachloroauric acid can also be used for gold plating .

safety

If tetrachloroauric acid gets on the skin, it is corroded and blistered. Irradiation of light on the affected area turns it purple.

Individual evidence

↑ ^a ^b ^c ^d ^e ^f Entry on tetrachloroauric (III) acid in the GESTIS substance database of the IFA , accessed on January 8, 2018(JavaScript required) .
↑ ^a ^b ^c ^d ^e Entry on gold connections. In: Römpp Online . Georg Thieme Verlag, accessed on May 25, 2014.
↑ Georg Brauer (Ed.), With the collaboration of Marianne Baudler a . a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume II, Ferdinand Enke, Stuttgart 1978, ISBN 3-432-87813-3 , p. 1014.

[GESTIS-1] ↑ ^a ^b ^c ^d ^e ^f Entry on tetrachloroauric (III) acid in the GESTIS substance database of the IFA , accessed on January 8, 2018(JavaScript required) .

[roempp-2] Entry on gold connections. In: Römpp Online . Georg Thieme Verlag, accessed on May 25, 2014.

[brauer-3] Georg Brauer (Ed.), With the collaboration of Marianne Baudler a . a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume II, Ferdinand Enke, Stuttgart 1978, ISBN 3-432-87813-3 , p. 1014.