Editing Sodium amalgam

{{Short description|Alloy of mercury and sodium}}
[[File:72. Добивање натриум амалгам.ogg|thumb|right|Synthesis of sodium amalgam]]
'''Sodium amalgam''', with the common formula Na(Hg), is an [[alloy]] of [[mercury (element)|mercury]] and [[sodium]]. The term [[amalgam (chemistry)|amalgam]] is used for alloys, [[intermetallic compound]]s, and solutions (both solid solutions and liquid solutions) involving mercury as a major component.  Sodium amalgams are often used in reactions as strong reducing agents with better handling properties compared to solid sodium.  They are less dangerously reactive toward water and in fact are often used as an aqueous suspension.

Sodium amalgam was used as a reagent as early as 1862.<ref>{{cite journal |last1=Atkinson |first1=E. |title=XLI. Chemical notices from foreign journals |journal=The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science |date=1862 |volume=24 |issue=161 |pages=305–311 |doi=10.1080/14786446208643359 }}</ref> A synthesis method was described by J. Alfred Wanklyn in 1866.<ref>{{cite journal |last1=Wanklyn |first1=J. Alfred |title=XII.—On a new method of forming organo-metallic bodies |journal=J. Chem. Soc. |date=1866 |volume=19 |pages=128–130 |doi=10.1039/JS8661900128 |url=https://zenodo.org/record/1734080}}</ref>

==Structure and compositions==
No particular formula is assigned to "sodium amalgam". Na<sub>5</sub>Hg<sub>8</sub> and Na<sub>3</sub>Hg are well defined compounds. In sodium amalgams, the Hg-Hg distances are expanded to around 5 [[Angstrom|Å]] vs. about 3 Å for mercury itself.<ref>{{Greenwood&Earnshaw2nd}}</ref> Usually amalgams are classified on the [[weight percent]] of sodium. Amalgams with 2% Na are solids at room temperature, whereas some more dilute amalgams remain liquid.<ref>Keith R. Buszek "Sodium Amalgam" in Encyclopedia of Reagents for Organic Synthesis, 2001, John Wiley.
{{doi|10.1002/047084289X.rs040}}</ref>

[[File:NaHg phase diagram.png|thumb|Phase diagram of sodium-mercury alloy system.]]

==Preparation==
{{external media
| topic = Demonstration and commentary on the preparation of sodium amalgam
| headerimage= [[File:YouTube 2024.svg|alt=YouTube logo|x15px|right]]
| caption = via [[YouTube]]
| video1 = [https://youtube.com/watch?v=SoOyaDWIoMA Mixing sodium with mercury] (31&nbsp;December 2018), by [[NileRed]]
}}

Metallic sodium dissolves in mercury [[exothermic]]ally, i.e. with the release of heat, therefore, formation of sodium amalgam is famously dangerous for generating sparks.<ref>{{OrgSynth | collvol = 2 | collvolpages = 607 | year = 1993 | title = Sodium triphenylmethyl | author = W.4r B. Renfrow Jr and C. R. Hauser | prep = cv2p0607}}</ref> The process causes localised boiling of the mercury and for this reason the formation is usually conducted in a fume hood and often performed using [[air-free technique]]s, such as synthesis under anhydrous liquid paraffin. Sodium amalgam may be prepared in the laboratory by dissolving sodium metal in mercury or the reverse.<ref>3% Na in Hg: {{cite book | doi = 10.1002/9780470132326.ch4 | author = Babcock, S. H. | volume = 1 | pages = 10–11 | last2 = Lankelma | first2 = H. P. | last3 = Vopicka | first3 = E. | title = Inorganic Syntheses | chapter = Sodium Amalgam | date = 2007 | isbn = 978-0-470-13232-6}}</ref><ref>see the notes in {{OrgSynth | collvol = 6 | collvolpages = 461 | year = 1988 | title = trans-3,5-Cyclohexadiene-1,2-dicarboxylic acid | author = Richard N. McDonald and Charles E. Reineke | prep = cv6p0461}}</ref><ref>Procedure for making Na(Hg) by addition of Na to Hg: {{OrgSynth | collvol = 8 | collvolpages = 479 | year = 1993 | title = Vinylation of Enolates with a Vinyl Cation Equivalent | author = Tony C. T. Chang, Myron Rosenblum, and Nancy Simms | prep = cv8p0479}}</ref> Sodium amalgams can be purchased from chemical supply houses.

==Uses==
Sodium amalgam has been used in [[organic chemistry]] as a powerful [[reducing agent]], which is safer to handle than sodium itself. It is used in [[Emde degradation]], and also for reduction of aromatic ketones to hydrols.<ref>{{Cite journal|last=Bachmann|first=W. E.|date=February 1933|title=The Mechanism of Reduction by Sodium Amalgam and Alcohol. I. The Reduction of Aromatic Ketones to Hydrols|journal=Journal of the American Chemical Society|language=en|volume=55|issue=2|pages=770–774|doi=10.1021/ja01329a051|issn=0002-7863}}</ref>

A sodium amalgam is used in the design of the [[Sodium vapor lamp|high pressure sodium lamp]] providing sodium to produce the proper color, and mercury to tailor the electrical characteristics of the lamp.

===Mercury cell electrolysis===
Sodium amalgam is a [[by-product]] of [[chlorine]] made by [[mercury cell electrolysis]]. In this cell, [[brine]] (concentrated [[sodium chloride]] solution) is [[electrolysis|electrolysed]] between a liquid mercury [[cathode]] and a [[titanium]] or [[graphite]] [[anode]]. Chlorine is formed at the anode, while sodium formed at the cathode dissolves into the mercury, making sodium amalgam. Normally this sodium amalgam is drawn off and reacted with water in a "decomposer cell" to produce [[hydrogen]] gas, concentrated [[sodium hydroxide]] solution, and mercury to be recycled through the process. In principle, all the mercury should be completely recycled, but inevitably a small portion goes missing. Because of concerns about this mercury escaping into the environment, the mercury cell process is generally being replaced by plants which use a less toxic cathode.

==References==
<references/>

==External links==
* [http://msds.chem.ox.ac.uk/SO/sodium-mercury_amalgam.html Oxford MSDS] {{Webarchive|url=https://web.archive.org/web/20111217022434/http://msds.chem.ox.ac.uk/SO/sodium-mercury_amalgam.html |date=2011-12-17 }}

{{Mercury compounds}}

[[Category:Reducing agents]]
[[Category:Sodium alloys]]
[[Category:Amalgams]]

[[de:Amalgam#Natriumamalgam]]