text:
Aqua regia
From Wikipedia, the free encyclopedia
Jump to: navigation, search
Aqua regia[note 1]
Names
IUPAC name
nitric acid hydrochloride
Other names
aqua regis, nitrohydrochloric acid
Identifiers
CAS Number
8007-56-5
3D model (JSmol)
Interactive image
PubChem CID
62687
SMILES[show]
[N+](=O)(O)[O-].Cl
Properties
Chemical formula
HNO3+3 HCl
Appearance red, yellow or gold fuming liquid
Density 1.01–1.21 g/cm3
Melting point −42 °C (−44 °F; 231 K)
Boiling point 108 °C (226 °F; 381 K)
Solubility in water
miscible in water
Vapor pressure 21 mbar
Hazards
NFPA 704
0
3
0
OX
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references
Freshly prepared aqua regia to remove metal salt deposits
Freshly prepared aqua regia is colorless, but it turns orange within seconds. Here, fresh aqua regia has been added to these NMR tubes to remove all traces of organic material.
Aqua regia /ˈa.kʷə ˈɹeɪ.gi.ə/ (from Latin, lit. "royal water" or "king's water") is a mixture of nitric acid and hydrochloric acid,[1] optimally in a molar ratio of 1:3. Aqua regia is a yellow-orange fuming liquid, so named by alchemists because it can dissolve the noble metals gold and platinum, though not all metals.
Contents
[hide]
1 Applications
2 Chemistry
2.1 Dissolving gold
2.2 Dissolving platinum
2.3 Reaction with tin
2.4 Decomposition of aqua regia
3 History
4 See also
5 Notes
6 References
7 External links
Applications[edit]
Aqua regia is primarily used to produce chloroauric acid, the electrolyte in the Wohlwill process for refining the highest quality (99.999%) gold.
Aqua regia is also used in etching and in specific analytic procedures. It is also used in some laboratories to clean glassware of organic compounds and metal particles. This method is preferred over the more traditional chromic acid bath for cleaning NMR tubes, because no traces of paramagnetic chromium can remain to spoil spectra.[2] While chromic acid baths are discouraged because of the high toxicity of chromium and the potential for explosions, aqua regia is itself very corrosive and has been implicated in several explosions due to mishandling.[3]
Due to the reaction between its components resulting in its decomposition, aqua regia quickly loses its effectiveness (yet remains a strong acid), so its components are usually only mixed immediately before use.
While local regulations may vary, aqua regia may be disposed of by careful neutralization, before being poured down the sink. If there is contamination by dissolved metals, the neutralized solution should be collected for disposal.[4][5]
Chemistry[edit]
Dissolving gold[edit]
Pure gold precipitate produced by the aqua regia chemical refining process
Aqua regia dissolves gold, though neither constituent acid will do so alone, because, in combination, each acid performs a different task. Nitric acid is a powerful oxidizer, which will actually dissolve a virtually undetectable amount of gold, forming gold ions (Au3+). The hydrochloric acid provides a ready supply of chloride ions (Cl−), which react with the gold ions to produce tetrachloroaurate(III) anions, also in solution. The reaction with hydrochloric acid is an equilibrium reaction that favors formation of chloroaurate anions (AuCl4−). This results in a removal of gold ions from solution and allows further oxidation of gold to take place. The gold dissolves to become chloroauric acid. In addition, gold may be dissolved by the free chlorine present in aqua regia. Appropriate equations are:
Au + 3 HNO
3 + 4 HCl ↽ − ⇀ {\displaystyle {\ce {<=>>}}} [AuCl
4]−
+ 3 [NO
2] + [H
3O]+
+ 2 H
2O
or
Au + HNO
3 + 4 HCl ↽ − ⇀ {\displaystyle {\ce {<=>>}}} [AuCl
4]−
+ [NO] + [H
3O]+
+ H
2O
If the aqua regia solution only contains gold, solid tetrachloroauric acid may be prepared by boiling off excess aqua regia, and removing residual nitric acid by repeatedly heating with hydrochloric acid. That step reduces nitric acid (see decomposition of aqua regia). If elemental gold is desired, it may be selectively reduced with sulfur dioxide, hydrazine, oxalic acid, etc.[6] Appropriate equations are, for example:
2 AuCl−
4 (aq) + 3 SO
2(g) + 6 H
2O (l) → 2 Au (s) + 12 H+
(aq) + 3 SO2−
4(aq) + 8 Cl−
(aq).
Dissolving platinum[edit]
Similar equations can be written for platinum. As with gold, the oxidation reaction can be written with either nitric oxide or nitrogen dioxide as the nitrogen oxide product.
Pt (s) + 4 NO−
3 (aq) + 8 H+ (aq) → Pt4+ (aq) + 4 NO2 (g) + 4 H2O (l)
3Pt (s) + 4 NO−
3 (aq) + 16 H+ (aq) → 3Pt4+ (aq) + 4 NO (g) + 8 H2O (l)
The oxidized platinum ion then reacts with chloride ions resulting in the chloroplatinate ion.
Pt4+ (aq) + 6 Cl− (aq) → PtCl2−
6 (aq)
Experimental evidence reveals that the reaction of platinum with aqua regia is considerably more complex. The initial reactions produce a mixture of chloroplatinous acid (H2PtCl4) and nitrosoplatinic chloride ((NO)2PtCl4). The nitrosoplatinic chloride is a solid product. If full dissolution of the platinum is desired, repeated extractions of the residual solids with concentrated hydrochloric acid must be performed.
2Pt (s) + 2HNO3 (aq) + 8 HCl (aq) → (NO)2PtCl4 (s) + H2PtCl4 (aq) + 4 H2O (l)
(NO)2PtCl4 (s) + 2 HCl (aq) ⇌ H2PtCl4 (aq) + 2 NOCl (g)
The chloroplatinous acid can be oxidized to chloroplatinic acid by saturating the solution with chlorine while heating.
H2PtCl4 (aq) + Cl2 (g) → H2PtCl6 (aq)
Dissolving platinum solids in aqua regia was the mode of discovery for the most dense metals, iridium and osmium, both of which are found in platinum ore and will not be dissolved by the acid, instead collecting on the base of the vessel.
As a practical matter, when platinum group metals are purified through dissolution in aqua regia, gold (commonly associated with PGMs) is precipitated by treatment with iron(II) chloride. Platinum in the filtrate, as hexachloroplatinate(VI), is converted to ammonium hexachloroplatinate by the addition of ammonium chloride. This ammonium salt is extremely insoluble, and it can be filtered off. Ignition (strong heating) converts it to platinum metal:[7]
3 (NH4)2PtCl6 → 3 Pt + 2 N2 + 2 NH4Cl + 16 HCl
Unprecipitated hexachloroplatinate(IV) is reduced with elemental zinc, and a similar method is suitable for small scale recovery of platinum from laboratory residues.[8]
A platinum Soviet commemorative coin being dissolved in aqua regia.
Reaction with tin[edit]
Aqua regia reacts with tin to form tin(IV) chloride, containing tin in its highest oxidation state:
4 HCl + 2 HNO3 + Sn → SnCl4 + NO2 + NO + 3 H2O
Decomposition of aqua regia[edit]
Upon mixing of concentrated hydrochloric acid and concentrated nitric acid, chemical reactions occur. These reactions result in the volatile products nitrosyl chloride and chlorine as evidenced by the fuming nature and characteristic yellow color of aqua regia. As the volatile products escape from solution, the aqua regia loses its potency.
HNO3 (aq) + 3 HCl (aq) → NOCl (g) + Cl2 (g) + 2 H2O (l)
Nitrosyl chloride can further decompose into nitric oxide and chlorine. This dissociation is equilibrium-limited. Therefore, in addition to nitrosyl chloride and chlorine, the fumes over aqua regia contain nitric oxide.
2 NOCl (g) → 2 NO (g) + Cl2 (g)
Because nitric oxide reacts readily with atmospheric oxygen, the gases produced also contain nitrogen dioxide, NO2.
2 NO (g) + O2 (g) → 2 NO2 (g)
History[edit]
The fox in Basil Valentine's Third Key represents aqua regia, Musaeum Hermeticum, 1678
Aqua regia was first prepared by a Persian-Arab[9][10][11] alchemist Jabir Ibn Al-Hayyan in the 8th century AD by dissolving ammonium chloride into nitric acid. It later appeared in a work of Pseudo-Geber dated to the early 14th century.[12] The third of Basil Valentine's keys shows a dragon in the foreground and a fox eating a rooster in the background. The rooster symbolizes gold (from its association with sunrise and the sun’s association with gold), and the fox represents aqua regia. The repetitive dissolving, heating, and redissolving (the rooster eating the fox eating the rooster) leads to the buildup of chlorine gas in the flask. The gold then crystallizes in the form of gold(III) chloride, whose red crystals were known as dragon's blood.[citation needed] The reaction was not reported in modern chemical literature until 1890.[12]
Antoine Lavoisier called aqua regia nitro-muriatic acid in 1789.[13]
When Germany invaded Denmark in World War II, Hungarian chemist George de Hevesy dissolved the gold Nobel Prizes of German physicists Max von Laue (1914) and James Franck (1925) in aqua regia to prevent the Nazis from confiscating them. The German government had prohibited Germans from accepting or keeping any Nobel Prize after jailed peace activist Carl von Ossietzky had received the Nobel Peace Prize in 1935. De Hevesy placed the resulting solution on a shelf in his laboratory at the Niels Bohr Institute. It was subsequently ignored by the Nazis who thought the jar—one of perhaps hundreds on the shelving—contained common chemicals. After the war, de Hevesy returned to find the solution undisturbed and precipitated the gold out of the acid. The gold was returned to the Royal Swedish Academy of Sciences and the Nobel Foundation. They re-cast the medals and again presented them to Laue and Franck.[14][15]
See also[edit]
Aqua fortis
Digger gold
Notes[edit]
Jump up ^ The information in the infobox is only accurate if the molar ratio of nitric acid to hydrochloric acid is 1:3.
References[edit]
Jump up ^ The relative concentrations of the two acids in water differ, values could be 65% w/v for nitric acid and 35% w/v for hydrochloric acid — that is, the actual HNO3:HCl mass ratio is less than 1:2,
Jump up ^ Hoffman, R. (10 March 2005) How to make an NMR sample, Hebrew University. Accessed 31 October 2006.
Jump up ^ American Industrial Hygiene Association, Laboratory Safety Incidents: Explosions. Accessed 8 September 2010.
Jump up ^ Committee on Prudent Practices for Handling, Storage, and Disposal of Chemicals in Laboratories, National Research Council (1995). Prudent Practices in the Laboratory: Handling and Disposal of Chemicals (free fulltext). National Academies Press. pp. 160–161. CS1 maint: Uses authors parameter (link)
Jump up ^ "Aqua Regia". Laboratory Safety Manual. Princeton University.
Jump up ^ Renner, Hermann; Schlamp, Günther; Hollmann, Dieter; Lüschow, Hans Martin; Tews, Peter; Rothaut, Josef; Dermann, Klaus; Knödler, Alfons; et al. (2005), "Gold, Gold Alloys, and Gold Compounds", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a12_499
Jump up ^ Hunt, L. B.; Lever, F. M. (1969). "Platinum Metals: A Survey of Productive Resources to industrial Uses" (PDF). Platinum Metals Review. 13 (4): 126–138.
Jump up ^ Kauffman, George B.; Teter, Larry A.; Rhoda, Richard N. (1963). "Recovery of Platinum from Laboratory Residues". Inorg. Synth. Inorganic Syntheses. 7: 232. doi:10.1002/9780470132388.ch61. ISBN 9780470132388.
Jump up ^ Kraus, P. (1962). "Djābir B. Ḥayyān". Encyclopaedia of Islam. 2 (2nd ed.). Brill Academic Publishers. pp. 357–359. As for Djābir's historic personality, Holmyard has suggested that his father was "a certain Azdī called Hayyan, druggist of Kufa... mentioned... in connection with the political machinations that were used by many people, in the eighth century, finally resulted in the overthrow of the Umayyad dynasty.
Jump up ^ Holmyard, Eric John, "Introduction" to The Works of Geber, translated by Richard Russell (London: Dent, 1928), p. vii: "Abu Musa Jabir ibn Hayyan, generally known merely as Jabir, was the son of a druggist belonging to the famous South Arabian tribe of Al-Azd. Members of this tribe had settled at the town of Kufa, in Iraq, shortly after the Muhammadan conquest in the seventh century A.D., and it was in Kufa that Hayyan the druggist lived."
Jump up ^ https://archive.org/details/WorksOfGeber
^ Jump up to: a b Principe, Lawrence M. (2012). The secrets of alchemy. Chicago: University of Chicago Press. ISBN 0226682951.
Jump up ^ Lavoisier, Antoine (1790). Elements of Chemistry, in a New Systematic Order, Containing All the Modern Discoveries. Edinburgh: William Creech. p. 116. ISBN 978-0486646244.
Jump up ^ "Adventures in radioisotope research", George Hevesy
Jump up ^ Birgitta Lemmel (2006). "The Nobel Prize Medals and the Medal for the Prize in Economics". The Nobel Foundation.
External links[edit]
Chemistry Comes Alive! Aqua Regia
Aqua Regia at The Periodic Table of Videos (University of Nottingham)
Demonstration of Gold Coin Dissolving in Acid (Aqua Regia)
Authority control
GND: 4365575-0
Retrieved from "https://en.wikipedia.org/w/index.php?title=Aqua_regia&oldid=825493600"
Categories:
Gold
Alchemical substances
Oxidizing mixtures
Oxidizing acids
Mineral acids
Iranian inventions
Hidden categories:
CS1 maint: Uses authors parameter
Articles without InChI source
Chemical pages without ChemSpiderID
Articles without EBI source
Articles without KEGG source
Articles without UNII source
Articles containing unverified chemical infoboxes
All articles with unsourced statements
Articles with unsourced statements from November 2017
Wikipedia articles with GND identifiers
Navigation menu
Personal tools
Not logged in
Talk
Contributions
Create account
Log in
Namespaces
Article
Talk
Variants
Views
Read
Edit
View history
More
Search
Navigation
Main page
Contents
Featured content
Current events
Random article
Donate to Wikipedia
Wikipedia store
Interaction
Help
About Wikipedia
Community portal
Recent changes
Contact page
Tools
What links here
Related changes
Upload file
Special pages
Permanent link
Page information
Wikidata item
Cite this page
Print/export
Create a book
Download as PDF
Printable version
In other projects
Wikimedia Commons
Languages
Afrikaans
العربية
تۆرکجه
Беларуская
Български
Bosanski
Català
Čeština
Dansk
Deutsch
Eesti
Ελληνικά
Español
Esperanto
فارسی
Français
한국어
Հայերեն
हिन्दी
Hrvatski
Bahasa Indonesia
Íslenska
Italiano
עברית
ಕನ್ನಡ
Latina
Latviešu
Lietuvių
Lumbaart
Magyar
മലയാളം
Bahasa Melayu
Монгол
Nederlands
日本語
Norsk
Norsk nynorsk
Occitan
Polski
Português
Română
Русский
Scots
Shqip
Simple English
Slovenčina
Slovenščina
Српски / srpski
Srpskohrvatski / српскохрватски
Suomi
Svenska
தமிழ்
తెలుగు
Türkçe
Українська
Tiếng Việt
粵語
中文
Edit links
This page was last edited on 13 February 2018, at 18:31.
Text is available under the Creative Commons Attribution-ShareAlike License; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization.
Privacy policy
About Wikipedia
Disclaimers
Contact Wikipedia
Developers
Cookie statement
Mobile view
Enable previews

values: mw-page-base noprint

values: mw-head-base noprint

values: firstHeading firstHeading en

values: siteSub noprint

values: jump-to-nav mw-jump

value: sup

value: caption

value: img

attrs: href class

values: background: #f8eaba; text-align: center;

attrs: href title

values: chemapps.stolaf.edu (3D interactive model)

values: Simplified molecular-input line-entry system

values: font-size: 105%; text-align:left; font-weight:normal; background:transparent;

values: border-top:1px solid #ccc; padding:0.2em 0 0.2em 1.6em; word-wrap:break-word; text-indent:-1.5em; text-align:left; font-size:11px; line-height:120%;

values: list-style: none none; margin-left: 0px; word-break: break-all; font-size: 105%; margin-top: 0px; margin-bottom: 0px; line-height: inherit; display: none;

values:
NavFrame collapsed
border: none; padding: 0;
NavFrame1

values: Flammability code 0: Will not burn. E.g., water

values: Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas

values: Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen

values: Special hazard OX: Oxidizer. E.g., potassium perchlorate

attrs: alt src width height srcset data-file-width data-file-height usemap

values: width:12px; text-align:center; position:absolute; top:12px; left:35px;

values: width:13px; text-align:center; position:absolute; top:31px; left:15px;

values: width:13px; text-align:center; position:absolute; top:31px; left:54px;

values: font-size:15px; color:black; width:23px; position:absolute; left:29px;

values: vertical-align:middle; text-align:center; line-height:80%; position:absolute; top:52px;

values: width:100%; background:transparent; margin:0 auto; width:82px; font-family:sans-serif background:; float:left; font-size:20px; text-align:center; vertical-align:middle; position:relative; height:80px; width:80px; padding:1px;

values: margin:0 auto; text-align:left; padding:0.1em 0;line-height:1.2em;

values: background:#f8eaba; border-top:2px solid transparent;

values: width:40%; max-height:1px; border-top:2px solid transparent; border-right:1px solid transparent;

values: width:60%; max-height:1px; border-top:2px solid transparent; border-left:1px solid transparent;

values: Representation in the International Phonetic Alphabet (IPA)

values: vertical-align: 0; margin-bottom: -0.338ex; width:3.358ex; height:2.676ex;

values:
/wiki/Tetrachloroauric_acid
mw-redirect
Tetrachloroauric acid

values: Plaatina reageerimine kuningveega 02.JPG

values: Plaatina reageerimine kuningveega 03.JPG

values: Edit section: Decomposition of aqua regia

values: This claim needs references to reliable sources. (November 2017)

values:
noprint Inline-Template Template-Fact
white-space:nowrap;

values:
/wiki/Aqua_fortis
mw-redirect
Aqua fortis

values:
reflist mw-references-wrap
list-style-type: decimal;

values:
/wiki/Hebrew_University
mw-redirect
Hebrew University

values: Category:CS1 maint: Uses authors parameter

values:
nofollow
external text
//doi.org/10.1002%2F14356007.a12_499

values:
nofollow
external text
//doi.org/10.1002%2F9780470132388.ch61

values: -moz-column-width: 30em; -webkit-column-width: 30em; column-width: 30em; list-style-type: decimal;

values:
/wiki/The_Periodic_Table_of_Videos
mw-redirect
The Periodic Table of Videos

values:
nofollow
external text
https://d-nb.info/gnd/4365575-0

values: Category:Chemical pages without ChemSpiderID

values: Category:Articles containing unverified chemical infoboxes

values: Category:All articles with unsourced statements

values: Category:Articles with unsourced statements from November 2017

values: Category:Wikipedia articles with GND identifiers

values: Discussion about edits from this IP address [ctrl-alt-n]

values: A list of edits made from this IP address [ctrl-alt-y]

values: You are encouraged to create an account and log in; however, it is not mandatory

values: You're encouraged to log in; however, it's not mandatory. [ctrl-alt-o]

values:
/wiki/Aqua_regia
View the content page [ctrl-alt-c]
c

values: Discussion about the content page [ctrl-alt-t]

values: p-namespaces navigation vectorTabs p-namespaces-label

values:
p-variants
navigation
vectorMenu emptyPortlet
p-variants-label

values: Past revisions of this page [ctrl-alt-h]

values: p-views navigation vectorTabs p-views-label

values:
p-cactions
navigation
vectorMenu emptyPortlet
p-cactions-label

values:
mw-wiki-logo
/wiki/Main_Page
Visit the main page

values:
/wiki/Main_Page
Visit the main page [ctrl-alt-z]
z

values: Featured content – the best of Wikipedia

values: Find background information on current events

values:
/wiki/Special:Random
Load a random article [ctrl-alt-x]
x

values: portal navigation p-navigation p-navigation-label

values: Guidance on how to use and edit Wikipedia

values: About the project, what you can do, where to find things

values: A list of recent changes in the wiki [ctrl-alt-r]

values: portal navigation p-interaction p-interaction-label

values: List of all English Wikipedia pages containing links to this page [ctrl-alt-j]

values: Recent changes in pages linked from this page [ctrl-alt-k]

values: ماء ملكي – Arabic

values: Царская гарэлка – Belarusian

values: Царска вода – Bulgarian

values:
https://da.wikipedia.org/wiki/Kongevand
Kongevand – Danish
da
da
interlanguage-link-target

values: Βασιλικό νερό – Greek

values: تیزاب سلطانی – Persian

values: Արքայաջուր – Armenian

values: अम्लराज – Hindi

values:
https://id.wikipedia.org/wiki/Air_raja
Air raja – Indonesian
id
id
interlanguage-link-target

values: מי מלך – Hebrew

values: ರಾಜೋದಕ – Kannada

values: അക്വാ റീജിയ – Malayalam

values: Хаан дарс – Mongolian

values:
https://no.wikipedia.org/wiki/Kongevann
Kongevann – Norwegian
no
no
interlanguage-link-target

values:
https://nn.wikipedia.org/wiki/Kongevatn
Kongevatn – Norwegian Nynorsk
nn
nn
interlanguage-link-target

values: Царская водка – Russian

values: Царска вода – Serbian

values: இராச திராவகம் – Tamil

values: అక్వారిజియా – Telugu

values:
https://tr.wikipedia.org/wiki/Kral_suyu
Kral suyu – Turkish
tr
tr
interlanguage-link-target

values: Царська вода – Ukrainian

values:
suggestions
display: none; font-size: 13px;

values: mediawiki ltr sitedir-ltr mw-hide-empty-elt ns-0 ns-subject page-Aqua_regia rootpage-Aqua_regia skin-vector action-view