Nitratoauric acid

Nitratoauric acid

Names
IUPAC name Hydrogen tetranitratoaurate(III)[1]
Other names Gold(III) nitrate Auronitric acid Gold(III) hydrogen nitrate Aurinitric acid
Identifiers
CAS Number	13464-77-2
ChemSpider	21241708
EC Number	236-687-0
PubChem CID	102601521
Properties
Chemical formula	HAu(NO3)4
Molar mass	445.99 g/mol (anhydrous) 500.04 g/mol (trihydrate)
Appearance	Brown Crystals[1]
Density	2.84 g/cm^3[1]
Melting point	72.6 °C (162.7 °F; 345.8 K)[2]
Solubility in water	Hydrolyzes[2]
Solubility in nitric acid	Insoluble (0 °C) Soluble (30 °C)
Structure[2]
Crystal structure	Monoclinic
Space group	C2/c
Lattice constant	a = 1214.5 pm, b = 854.4 pm, c = 1225.7 pm
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Oxidizing
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H272, H302, H312, H315, H318, H332, H335
Precautionary statements	P210, P220, P221, P261, P280, P302+P352, P304+P340, P305+P351+P338, P332+P313
NFPA 704 (fire diamond)	1 0 2 OX
Related compounds
Other anions	Chloroauric acid
Other cations	Potassium tetranitratoaurate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Nitratoauric acid, hydrogen tetranitratoaurate, or simply called gold(III) nitrate is a crystalline gold compound that forms the trihydrate, HAu(NO₃)₄·3H₂O or more correctly H₅O₂Au(NO₃)₄·H₂O.^[3][2] This compound is an intermediate in the process of extracting gold.^[4] In older literature it is also known as aurinitric acid.^[5]

Preparation and reactions

Nitratoauric acid is prepared by the reaction of gold(III) hydroxide and concentrated nitric acid at 100 °C:^[2][5]

Au(OH)₃ + 4HNO₃ → HAu(NO₃)₄ + 3 H₂O

This compound reacts with potassium nitrate to form potassium tetranitratoaurate at 0 °C:^[6]

HAu(NO₃)₄ + KNO₃ → KAu(NO₃)₄ + HNO₃

Properties

Nitratoauric acid trihydrate decomposes to the monohydrate at 72 °C. If continually heated to 203 °C, it decomposes to auric oxide.^[2]

Simple gold(III) nitrate

The production of the simple nitrate (Au(NO₃)₃) was reported from the reaction of gold oxide and dinitrogen pentoxide, however, this was later proven to be nitronium tetranitratoaurate ((NO₂)Au(NO₃)₄).^[7][8]

However, the ammine complex of the simple gold nitrate is known. Au(NH₃)₄(NO₃)₃, also known as tetraaminegold(III) nitrate, is produced by the addition of ammonium nitrate to a solution of chloroauric acid. The hydrolysis of this compound produces fulminating gold.^[9][10][11]

References

1. "Gold Nitrate". ESPI Metals.
2. Oliver Büchner; Mathias S. Wickleder (2004). "Tetranitratogoldsäure, (H₅O₂)[Au(NO₃)₄]·H₂O: Synthese, Kristallstruktur und thermisches Verhalten des ersten sauren Nitrates des Goldes". Zeitschrift für anorganische und allgemeine Chemie (in German). 630 (7): 1079–1083. doi:10.1002/zaac.200400092.
3. A. Jamieson Walker (1924). The Alkali-metals and Their Congeners. the University of California: C. Griffin. p. 349.
4. D. P. Graddon; H. Taube; A. G. Maddock (2017). An Introduction to Co-Ordination Chemistry (Ebook) (2nd ed.). Elsevier Science. p. 148. ISBN 9781483184111.
5. Harry Mann Gordin (1913). Elementary Chemistry (1 ed.). the University of Wisconsin - Madison: Medico-dental Publishing Company. p. 437.
6. Ripan R., Chetyanu I. (1972). Inorganic chemistry. Chemistry of metals. Vol. 2. Moscow: World.
7. B. O. Field; C. J. Hardy (1964). "Volatile and anhydrous nitrato-complexes of metals: preparation by the use of dinitrogen pentoxide, and measurement of infrared spectra". Journal of the Chemical Society: 4428–4434. doi:10.1039/JR9640004428.
8. Mathias S. Wickleder; Oliver Büchner; Frauke Gerlach; Mandus Necke; Katharina Al-Shamery; Thomas Wich; Tim Luttermann (2008). "Synthesis, Characterization and Electron Beam Assisted Decomposition of (NO₂)[Au(NO₃)₄]". Chemistry of Materials. 20 (16): 5181–5185. doi:10.1021/cm800066r.
9. Weishaupt, Martin; Strähle, Joachim (1976). "Kristallstruktur und Schwingungsspektrum des Tetrammingold(III) -nitrats" [Crystal Structure and Vibrational Spectrum of Tetraamminegold(III)-Nitrate]. Zeitschrift für Naturforschung B (in German). 31 (5): 554–557. doi:10.1515/znb-1976-0505.
10. Skibsted, L. H.; Bjerrum, Jannik (1974). "Studies on Gold Complexes. I. Robustness, Stability and Acid Dissociation of the Tetramminegold(III) Ion". Acta Chemica Scandinavica. 28: 740–746. doi:10.3891/acta.chem.scand.28a-0740.
11. Michel Manfait; Alain J.P. Alix; Charles Kappenstein (1981). "Raman and infrared studies of the square planar tetraammine gold(III) nitrate and its deuterate". Inorganica Chimica Acta. 50: 147–152. doi:10.1016/S0020-1693(00)83735-4.