Sodium amalgam

Sodium amalgam

Sodium amalgam, commonly denoted Na(Hg), is an amalgam, or alloy of mercury, with sodium metal. When metallic sodium is dissolved in mercury, it reacts exothermically to produce the intermetallic compound NaHg2, with enough heat to cause localised boiling of the mercury. This process is normally performed under dry nitrogen gas. This compound is a spongey grey mass, but is also soluble in mercury, allowing a more dilute, liquid amalgam to be produced.

Preparation

Sodium amalgam may be prepared in the laboratory simply by dissolving sodium metal in mercury, under air-free conditions. [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] Alternatively, it may be purchased from chemical supply houses.

Uses

Since its introduction in the 1880s by students of Robert Bunsen, Julius Tafel and Hans Goldschmidt, sodium amalgam has also been used in organic chemistry as a powerful reducing agent which is safer to handle than sodium itself. An example of its use is in the Emde degradation.

A sodium amalgam is used in the design of the 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 manufactured by mercury cell electrolysis. In this cell, brine (concentrated sodium chloride solution) is 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 proportion 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

Further reading

*

External links

* [http://msds.chem.ox.ac.uk/SO/sodium-mercury_amalgam.html Oxford MSDS]


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  • Sodium amalgam — Sodium So di*um, n. [NL., fr.E. soda.] (Chem.) A common metallic element of the alkali group, in nature always occuring combined, as in common salt, in albite, etc. It is isolated as a soft, waxy, white, unstable metal, so highly reactive that it …   The Collaborative International Dictionary of English

  • sodium amalgam — noun an alloy of sodium and mercury; used as a powerful reducing agent, and in certain types of sodium lamp …   Wiktionary

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  • Sodium — So di*um, n. [NL., fr.E. soda.] (Chem.) A common metallic element of the alkali group, in nature always occuring combined, as in common salt, in albite, etc. It is isolated as a soft, waxy, white, unstable metal, so highly reactive that it… …   The Collaborative International Dictionary of English

  • Sodium carbonate — Sodium So di*um, n. [NL., fr.E. soda.] (Chem.) A common metallic element of the alkali group, in nature always occuring combined, as in common salt, in albite, etc. It is isolated as a soft, waxy, white, unstable metal, so highly reactive that it …   The Collaborative International Dictionary of English

  • Sodium chloride — Sodium So di*um, n. [NL., fr.E. soda.] (Chem.) A common metallic element of the alkali group, in nature always occuring combined, as in common salt, in albite, etc. It is isolated as a soft, waxy, white, unstable metal, so highly reactive that it …   The Collaborative International Dictionary of English

  • sodium hydrate — Sodium So di*um, n. [NL., fr.E. soda.] (Chem.) A common metallic element of the alkali group, in nature always occuring combined, as in common salt, in albite, etc. It is isolated as a soft, waxy, white, unstable metal, so highly reactive that it …   The Collaborative International Dictionary of English

  • Sodium hydroxide — Sodium So di*um, n. [NL., fr.E. soda.] (Chem.) A common metallic element of the alkali group, in nature always occuring combined, as in common salt, in albite, etc. It is isolated as a soft, waxy, white, unstable metal, so highly reactive that it …   The Collaborative International Dictionary of English

  • amalgam — /euh mal geuhm/, n. 1. an alloy of mercury with another metal or metals. 2. an alloy that consists chiefly of silver mixed with mercury and variable amounts of other metals and is used as a dental filling. 3. a rare mineral, an alloy of silver… …   Universalium

  • sodium — /soh dee euhm/, n. 1. Chem. a soft, silver white, metallic element that oxidizes rapidly in moist air, occurring in nature only in the combined state, and used in the synthesis of sodium peroxide, sodium cyanide, and tetraethyllead: a necessary… …   Universalium

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