Chloroauric acid is an inorganic compound with the chemical formulaH[AuCl4]. It forms hydrates H[AuCl4]·nH2O. Both the trihydrate and tetrahydrate are known. Both are orange-yellow solids consisting of the planar [AuCl4]− anion. Often chloroauric acid is handled as a solution, such as those obtained by dissolution of gold in aqua regia. These solutions can be converted to other gold complexes or reduced to metallic gold or gold nanoparticles.
The tetrahydrate crystallizes as [H5O2]+[AuCl4]− and two water molecules.[2] The oxidation state of gold in H[AuCl4] and [AuCl4]− anion is +3. The salts of H[AuCl4] (tetrachloroauric(III) acid) are tetrachloroaurates(III), containing [AuCl4]− anions (tetrachloroaurate(III) anions), which have square planar molecular geometry. The Au–Cl distances are around 2.28 Å. Other d8 complexes adopt similar structures, e.g. tetrachloroplatinate(II) [PtCl4]2−.
Solute properties
Solid chloroauric acid is a hydrophilic (ionic) protic solute. It is soluble in water and other oxygen-containing solvents, such as alcohols, esters, ethers, and ketones. For example, in dry dibutyl ether or diethylene glycol, the solubility exceeds 1 M.[3][4][5] Saturated solutions in the organic solvents often are the liquid solvates of specific stoichiometry. Chloroauric acid is a strong monoprotic acid.
When heated in air, solid H[AuCl4]·nH2O melts in the water of crystallization, quickly darkens and becomes dark brown.
Chemical reactions
Since [AuCl4]− is prone to hydrolyze,[6] upon treatment with an alkali metal base, chloroauric acid converts to gold(III) hydroxide.[7] The related thallium salt(Tl+[AuCl4]−) is poorly soluble in all nonreacting solvents. Salts of quaternary ammonium cations are known.[8] Other complex salts include [Au(bipy)Cl2]+[AuCl4]−[9] and [Co(NH3)6]3+[AuCl4]−(Cl−)2.
Partial reduction of chloroauric acid gives oxonium dichloridoaurate(1−).[10] Reduction may also yield other gold(I) complexes, especially with organic ligands. Often the ligand serves as reducing agent as illustrated with thiourea, CS(NH2)2:
Chloroauric acid is the precursor to gold nanoparticles by precipitation onto mineral supports.[11] Heating of H[AuCl4]·nH2O in a stream of chlorine gives gold(III) chloride (Au2Cl6).[12] Gold nanostructures can be made from chloroauric acid in a two-phase redox reaction whereby metallic clusters are amassed through the simultaneous attachment of self-assembled thiol monolayers on the growing nuclei. [AuCl4]− is transferred from aqueous solution to toluene using tetraoctylammonium bromide where it is then reduced with aqueous sodium borohydride in the presence of a thiol.[13]
Production
Chloroauric acid is produced by dissolving gold in aqua regia (a mixture of concentrated nitric and hydrochloric acids) followed by careful evaporation of the solution:[14][15]
Under some conditions, oxygen can be used as an oxidant.[16] For higher efficiency, these processes are conducted in autoclaves, which allows greater control of temperature and pressure. Alternatively, a solution of H[AuCl4] can be produced by electrolysis of gold metal in hydrochloric acid:
2 Au(s) + 8 HCl(aq) → 2 H[AuCl4](aq) + 3 H2(g)
To prevent the deposition of gold on the cathode, the electrolysis is carried out in a cell equipped with a membrane. This method is used for refining gold. Some gold remains in solution in the form of [AuCl2]−.[17]
Liquid–liquid extraction of chloroauric acid is used for the recovery, concentrating, purification, and analytical determinations of gold. Of great importance is the extraction of H[AuCl4] from hydrochloric medium by oxygen-containing extractants, such as alcohols, ketones, ethers and esters. The concentration of gold(III) in the extracts may exceed 1 mol/L.[3][4][5] Frequently used extractants for this purpose are dibutyl glycol, methyl isobutyl ketone, tributyl phosphate, dichlorodiethyl ether (chlorex).[18]
In histology, chlorauric acid is known as "brown gold chloride", and its sodium salt Na[AuCl4] (sodium tetrachloroaurate(III)) as "gold chloride", "sodium gold chloride" or "yellow gold chloride". The sodium salt is used in a process called "toning" to improve the optical definition of tissue sections stained with silver.[19]
Health effects and safety
Chloroauric acid is a strong eye, skin, and mucous membrane irritant. Prolonged skin contact with chloroauric acid may result in tissue destruction. Concentrated chloroauric acid is corrosive to skin and must, therefore, be handled with appropriate care, since it can cause skin burns, permanent eye damage, and irritation to mucous membranes. Gloves are worn when handling the compound.
^Williams, Jack Marvin; Peterson, Selmer Wiefred (1969). "Example of the [H5O2]+ ion. Neutron diffraction study of tetrachloroauric acid tetrahydrate". Journal of the American Chemical Society. 91 (3): 776–777. doi:10.1021/ja01031a062. ISSN 0002-7863.
^ abMironov, I. V.; Natorkhina, K. I. (2012). "On the selection of extractant for the preparation of high-purity gold". Russian Journal of Inorganic Chemistry. 57 (4): 610. doi:10.1134/S0036023612040195. S2CID 98015888.
^ abFeather, A.; Sole, K. C.; Bryson, L. J. (July 1997). "Gold refining by solvent extraction—the minataur process" (PDF). Journal of the Southern African Institute of Mining and Metallurgy: 169–173. Retrieved 2013-03-17.
^ abMorris, D. F. C.; Khan, M. A. (1968). "Application of solvent extraction to the refining of precious metals, Part 3: purification of gold". Talanta. 15 (11): 1301–1305. doi:10.1016/0039-9140(68)80053-0. PMID 18960433.
^Đurović, Mirjana D.; Puchta, Ralph; Bugarčić, Živadin D.; Eldik, Rudi van (1999-02-22). "Studies on the reactions of [AuCl4]− with different nucleophiles in aqueous solution". Dalton Transactions. 43 (23): 8620–8632. doi:10.1039/C4DT00247D. PMID 24760299. Retrieved 2021-12-07.
^Kawamoto, Daisuke; Ando, Hiroaki; Ohashi, Hironori; Kobayashi, Yasuhiro; Honma, Tetsuo; Ishida, Tamao; Tokunaga, Makoto; Okaue, Yoshihiro; Utsunomiya, Satoshi; Yokoyama, Takushi (2016-11-15). "Structure of a Gold(III) Hydroxide and Determination of Its Solubility". Bulletin of the Chemical Society of Japan. The Chemical Society of Japan. 89 (11): 1385–1390. doi:10.1246/bcsj.20160228. ISSN 0009-2673.
^Makotchenko, E. V.; Kokovkin, V. V. (2010). "Solid contact [AuCl4]−-selective electrode and its application for evaluation of gold(III) in solutions". Russian Journal of General Chemistry. 80 (9): 1733. doi:10.1134/S1070363210090021. S2CID 95581984.
^Mironov, I. V.; Tsvelodub, L. D. (2001). "Equilibria of the substitution of pyridine, 2,2′-bipyridyl, and 1,10-phenanthroline for Cl− in AuCl4− in aqueous solution". Russian Journal of Inorganic Chemistry. 46: 143–148.
^Huang, Xiaohua; Peng, Xianghong; Wang, Yiqing; Wang, Yuxiang; Shin, Dong M.; El-Sayed, Mostafa A.; Nie, Shuming (26 October 2010). "A reexamination of active and passive tumor targeting by using rod-shaped gold nanocrystals and covalently conjugated peptide ligands". ACS Nano. ACS Publications. 4 (10): 5887–5896. doi:10.1021/nn102055s. PMC2964428. PMID 20863096.
^Gunanathan, C.; Ben-David, Y.; Milstein, D. (2007). "Direct Synthesis of Amides from Alcohols and Amines with Liberation of H2". Science. 317 (5839): 790–792. Bibcode:2007Sci...317..790G. doi:10.1126/science.1145295. PMID 17690291. S2CID 43671648.
^Mellor, J. W. (1946). A Comprehensive Treatise on Inorganic and Theoretical Chemistry. vol. 3, p. 593.
^Brust, Mathias; Walker, Merryl; Bethell, Donald; Schiffrin, David J.; Whyman, Robin (1994). "Synthesis of Thiol-derivatised Gold Nanoparticles in a Two-phase Liquid-Liquid System". J. Chem. Soc., Chem. Commun. Royal Society of Chemistry (7): 801–802. doi:10.1039/C39940000801.
^Brauer, G., ed. (1963). Handbook of Preparative Inorganic Chemistry (2nd ed.). New York: Academic Press.
^Block, B. P. (1953). "Gold Powder and Potassium Tetrabromoaurate(III)". Inorganic Syntheses. Inorganic Syntheses. Vol. 4. pp. 14–17. doi:10.1002/9780470132357.ch4. ISBN9780470132357.
^Novoselov, R. I.; Makotchenko, E. V. (1999). "Application of oxygen as ecologically pure reagent for the oxidizing of non-ferrous and precious metals, sulphide minerals". Chemistry for Sustainable Development. 7: 321–330.
^Belevantsev, V. I.; Peschevitskii, B. I.; Zemskov, S. V. (1976). "New data on chemistry of gold compounds in solutions". Izvestiya Sibirskogo Otdeleniya AN SSSR, Ser. Khim. Nauk. 4 (2): 24–45.
^Hill JW, Lear TA (September 1988). "Recovery of gold from electronic scrap". J. Chem. Educ. 65 (9): 802. Bibcode:1988JChEd..65..802H. doi:10.1021/ed065p802.
^. Archived from the original on April 21, 2016. Retrieved April 14, 2016.
January 28, 2023
chloroauric, acid, inorganic, compound, with, chemical, formula, aucl4, forms, hydrates, aucl4, nh2o, both, trihydrate, tetrahydrate, known, both, orange, yellow, solids, consisting, planar, aucl4, anion, often, chloroauric, acid, handled, solution, such, thos. Chloroauric acid is an inorganic compound with the chemical formula H AuCl4 It forms hydrates H AuCl4 nH2O Both the trihydrate and tetrahydrate are known Both are orange yellow solids consisting of the planar AuCl4 anion Often chloroauric acid is handled as a solution such as those obtained by dissolution of gold in aqua regia These solutions can be converted to other gold complexes or reduced to metallic gold or gold nanoparticles Chloroauric acid NamesOther names Hydrogen tetrachloroaurateHydrogen tetrachloroaurate III Chlorauric acidTetrachloroauric III acidAurochloric acidAurate 1 tetrachloro hydrogen SP 4 1 Hydrogen aurichlorideIdentifiersCAS Number 16903 35 8 Y16961 25 4 trihydrate Y3D model JSmol Interactive imageChemSpider 26171 YECHA InfoCard 100 037 211EC Number 240 948 4PubChem CID 28133UNII 8H372EGX3V Y31KV0KH4AY trihydrate YCompTox Dashboard EPA DTXSID90156444InChI InChI 1S Au 4ClH h 4 1H q 3 p 3 YKey VDLSFRRYNGEBEJ UHFFFAOYSA K YInChI 1 Au 4ClH Na h 4 1H q 3 1 p 4 rAuCl4 Na c2 1 3 4 5 q 1 1Key IXPWAPCEBHEFOV ACHCXQQJAPInChI 1 Au 4ClH h 4 1H q 3 p 3 rAuCl4 c2 1 3 4 5 q 1 p 1Key VDLSFRRYNGEBEJ ZXMCYSOYAISMILES H Cl Au Cl Cl ClPropertiesChemical formula H AuCl4 Molar mass 339 785 g mol anhydrous 393 833 g mol trihydrate 411 85 g mol tetrahydrate Appearance orange yellow needle like hygroscopic crystalsDensity 3 9 g cm3 anhydrous 2 89 g cm3 tetrahydrate Melting point 254 C 489 F 527 K decomposes Solubility in water 350 g of H AuCl4 in 100 g of H2OSolubility soluble in alcohol ester ether ketonelog P 2 67510 1 Conjugate base Tetrachloroaurate III StructureCrystal structure monoclinicHazardsGHS labelling PictogramsSignal word DangerHazard statements H302 H314 H317 H373 H411Precautionary statements P260 P261 P264 P272 P280 P301 P330 P331 P302 P352 P303 P361 P353 P304 P340 P305 P351 P338 P310 P321 P333 P313 P363 P405 P501NFPA 704 fire diamond 301Safety data sheet SDS JT BakerRelated compoundsOther anions Tetrabromoauric acidRelated compounds Gold III chlorideExcept where otherwise noted data are given for materials in their standard state at 25 C 77 F 100 kPa N verify what is Y N Infobox references Contents 1 Properties 1 1 Structure 1 2 Solute properties 1 3 Chemical reactions 2 Production 3 Uses 4 Health effects and safety 5 ReferencesProperties EditStructure Edit The tetrahydrate crystallizes as H5O2 AuCl4 and two water molecules 2 The oxidation state of gold in H AuCl4 and AuCl4 anion is 3 The salts of H AuCl4 tetrachloroauric III acid are tetrachloroaurates III containing AuCl4 anions tetrachloroaurate III anions which have square planar molecular geometry The Au Cl distances are around 2 28 A Other d8 complexes adopt similar structures e g tetrachloroplatinate II PtCl4 2 Solute properties Edit Solid chloroauric acid is a hydrophilic ionic protic solute It is soluble in water and other oxygen containing solvents such as alcohols esters ethers and ketones For example in dry dibutyl ether or diethylene glycol the solubility exceeds 1 M 3 4 5 Saturated solutions in the organic solvents often are the liquid solvates of specific stoichiometry Chloroauric acid is a strong monoprotic acid When heated in air solid H AuCl4 nH2O melts in the water of crystallization quickly darkens and becomes dark brown Chemical reactions Edit Since AuCl4 is prone to hydrolyze 6 upon treatment with an alkali metal base chloroauric acid converts to gold III hydroxide 7 The related thallium salt Tl AuCl4 is poorly soluble in all nonreacting solvents Salts of quaternary ammonium cations are known 8 Other complex salts include Au bipy Cl2 AuCl4 9 and Co NH3 6 3 AuCl4 Cl 2 Partial reduction of chloroauric acid gives oxonium dichloridoaurate 1 10 Reduction may also yield other gold I complexes especially with organic ligands Often the ligand serves as reducing agent as illustrated with thiourea CS NH2 2 AuCl4 aq 3 CS NH2 2 s H2O l Au CS NH2 2 2 aq CO NH2 2 aq S s 2 Cl aq 2 HCl aq Chloroauric acid is the precursor to gold nanoparticles by precipitation onto mineral supports 11 Heating of H AuCl4 nH2O in a stream of chlorine gives gold III chloride Au2Cl6 12 Gold nanostructures can be made from chloroauric acid in a two phase redox reaction whereby metallic clusters are amassed through the simultaneous attachment of self assembled thiol monolayers on the growing nuclei AuCl4 is transferred from aqueous solution to toluene using tetraoctylammonium bromide where it is then reduced with aqueous sodium borohydride in the presence of a thiol 13 Production EditChloroauric acid is produced by dissolving gold in aqua regia a mixture of concentrated nitric and hydrochloric acids followed by careful evaporation of the solution 14 15 Au s HNO3 aq 4 HCl aq H AuCl4 aq NO g 2 H2O l Under some conditions oxygen can be used as an oxidant 16 For higher efficiency these processes are conducted in autoclaves which allows greater control of temperature and pressure Alternatively a solution of H AuCl4 can be produced by electrolysis of gold metal in hydrochloric acid 2 Au s 8 HCl aq 2 H AuCl4 aq 3 H2 g To prevent the deposition of gold on the cathode the electrolysis is carried out in a cell equipped with a membrane This method is used for refining gold Some gold remains in solution in the form of AuCl2 17 Uses EditChloroauric acid is the precursor used in the purification of gold by electrolysis Liquid liquid extraction of chloroauric acid is used for the recovery concentrating purification and analytical determinations of gold Of great importance is the extraction of H AuCl4 from hydrochloric medium by oxygen containing extractants such as alcohols ketones ethers and esters The concentration of gold III in the extracts may exceed 1 mol L 3 4 5 Frequently used extractants for this purpose are dibutyl glycol methyl isobutyl ketone tributyl phosphate dichlorodiethyl ether chlorex 18 In histology chlorauric acid is known as brown gold chloride and its sodium salt Na AuCl4 sodium tetrachloroaurate III as gold chloride sodium gold chloride or yellow gold chloride The sodium salt is used in a process called toning to improve the optical definition of tissue sections stained with silver 19 Health effects and safety EditChloroauric acid is a strong eye skin and mucous membrane irritant Prolonged skin contact with chloroauric acid may result in tissue destruction Concentrated chloroauric acid is corrosive to skin and must therefore be handled with appropriate care since it can cause skin burns permanent eye damage and irritation to mucous membranes Gloves are worn when handling the compound References Edit hydrogen tetrachloroaurate iii msds Williams Jack Marvin Peterson Selmer Wiefred 1969 Example of the H5O2 ion Neutron diffraction study of tetrachloroauric acid tetrahydrate Journal of the American Chemical Society 91 3 776 777 doi 10 1021 ja01031a062 ISSN 0002 7863 a b Mironov I V Natorkhina K I 2012 On the selection of extractant for the preparation of high purity gold Russian Journal of Inorganic Chemistry 57 4 610 doi 10 1134 S0036023612040195 S2CID 98015888 a b Feather A Sole K C Bryson L J July 1997 Gold refining by solvent extraction the minataur process PDF Journal of the Southern African Institute of Mining and Metallurgy 169 173 Retrieved 2013 03 17 a b Morris D F C Khan M A 1968 Application of solvent extraction to the refining of precious metals Part 3 purification of gold Talanta 15 11 1301 1305 doi 10 1016 0039 9140 68 80053 0 PMID 18960433 Đurovic Mirjana D Puchta Ralph Bugarcic Zivadin D Eldik Rudi van 1999 02 22 Studies on the reactions of AuCl4 with different nucleophiles in aqueous solution Dalton Transactions 43 23 8620 8632 doi 10 1039 C4DT00247D PMID 24760299 Retrieved 2021 12 07 Kawamoto Daisuke Ando Hiroaki Ohashi Hironori Kobayashi Yasuhiro Honma Tetsuo Ishida Tamao Tokunaga Makoto Okaue Yoshihiro Utsunomiya Satoshi Yokoyama Takushi 2016 11 15 Structure of a Gold III Hydroxide and Determination of Its Solubility Bulletin of the Chemical Society of Japan The Chemical Society of Japan 89 11 1385 1390 doi 10 1246 bcsj 20160228 ISSN 0009 2673 Makotchenko E V Kokovkin V V 2010 Solid contact AuCl4 selective electrode and its application for evaluation of gold III in solutions Russian Journal of General Chemistry 80 9 1733 doi 10 1134 S1070363210090021 S2CID 95581984 Mironov I V Tsvelodub L D 2001 Equilibria of the substitution of pyridine 2 2 bipyridyl and 1 10 phenanthroline for Cl in AuCl4 in aqueous solution Russian Journal of Inorganic Chemistry 46 143 148 Huang Xiaohua Peng Xianghong Wang Yiqing Wang Yuxiang Shin Dong M El Sayed Mostafa A Nie Shuming 26 October 2010 A reexamination of active and passive tumor targeting by using rod shaped gold nanocrystals and covalently conjugated peptide ligands ACS Nano ACS Publications 4 10 5887 5896 doi 10 1021 nn102055s PMC 2964428 PMID 20863096 Gunanathan C Ben David Y Milstein D 2007 Direct Synthesis of Amides from Alcohols and Amines with Liberation of H2 Science 317 5839 790 792 Bibcode 2007Sci 317 790G doi 10 1126 science 1145295 PMID 17690291 S2CID 43671648 Mellor J W 1946 A Comprehensive Treatise on Inorganic and Theoretical Chemistry vol 3 p 593 Brust Mathias Walker Merryl Bethell Donald Schiffrin David J Whyman Robin 1994 Synthesis of Thiol derivatised Gold Nanoparticles in a Two phase Liquid Liquid System J Chem Soc Chem Commun Royal Society of Chemistry 7 801 802 doi 10 1039 C39940000801 Brauer G ed 1963 Handbook of Preparative Inorganic Chemistry 2nd ed New York Academic Press Block B P 1953 Gold Powder and Potassium Tetrabromoaurate III Inorganic Syntheses Inorganic Syntheses Vol 4 pp 14 17 doi 10 1002 9780470132357 ch4 ISBN 9780470132357 Novoselov R I Makotchenko E V 1999 Application of oxygen as ecologically pure reagent for the oxidizing of non ferrous and precious metals sulphide minerals Chemistry for Sustainable Development 7 321 330 Belevantsev V I Peschevitskii B I Zemskov S V 1976 New data on chemistry of gold compounds in solutions Izvestiya Sibirskogo Otdeleniya AN SSSR Ser Khim Nauk 4 2 24 45 Hill JW Lear TA September 1988 Recovery of gold from electronic scrap J Chem Educ 65 9 802 Bibcode 1988JChEd 65 802H doi 10 1021 ed065p802 Silver Impregnation Archived from the original on April 21 2016 Retrieved April 14 2016 Retrieved from https en wikipedia org w index php title Chloroauric acid amp oldid 1132808112, wikipedia, wiki, book, books, library,
