Sodium acetate
1488243
220402364
2008-06-19T18:10:54Z
24.188.197.61
/* Preparation */
{{Chembox new
| Name = Sodium acetate
| ImageFile = Sodium-acetate-2D-skeletal.png
<!-- | ImageSize = 200px -->
| ImageName = Sodium acetate
| IUPACName = sodium acetate (IUPAC)<br />
sodium ethanoate (systematic)
| OtherNames = sodium salt
| Section1 = {{Chembox Identifiers
| CASOther = {{CAS|127-09-3}} (anhydrous)<br />{{CAS|6131-90-4}} (trihydrate)
}}
| Section2 = {{Chembox Properties
| Formula = CH<sub>3</sub>COONa
| MolarMass = 82.03 g/mol (anhydrous)<br />
136.08 g/mol (trihydrate)
| Appearance = White deliquescent powder
| Density = 1.45 g/cm³, solid
| Solubility = 76 g/100 ml (0°C)
| MeltingPt = Decomposes at 324 °C
| BoilingPt = Decomposes
| pKb = 9.25
}}
| Section3 = {{Chembox Structure
| CrystalStruct = [[monoclinic]]
| Dipole =
}}
| Section7 = {{Chembox Hazards
| ExternalMSDS = [http://www.jtbaker.com/msds/englishhtml/s2666.htm External MSDS]
| MainHazards = Irritant}}
}}
'''Sodium acetate''', (also '''sodium ethanoate''') is the [[sodium]] [[Salt (chemistry)|salt]] of [[acetic acid]]. It is an inexpensive chemical produced in industrial quantities for a wide range of uses.
==Applications==
Sodium acetate is used in the [[textile]] industry to neutralize [[sulfuric acid]] waste streams, and as a [[photoresist]] while using [[aniline dyes]]. It is also a [[pickling]] agent in chrome [[tanning]], and it helps to retard [[vulcanization]] of [[chloroprene]] in [[synthetic rubber]] production.
Sodium acetate is the chemical that gives salt and vinegar [[Potato chip|chips]] (crisps) their flavor. It may also be added to foods as a preservative; in this application it is usually written as "sodium diacetate" and labeled '''E262'''.
As the conjugate base of a weak acid, a solution of sodium acetate and acetic acid can act as a [[buffer solution|buffer]] to keep a relatively constant pH. This is useful especially in biochemical applications where reactions are pH dependent.
Sodium acetate is also used in consumer [[heating pad]]s or [[hand warmer]]s and is also used in "hot ice". When sodium acetate trihydrate crystals (melting point 58 °C) are heated to around 100 °C, they melt. When this melt cools, it gives a [[supersaturated]] solution of sodium acetate in water. This solution is capable of [[supercooling]] to room temperature, well below its melting point, without forming crystals. By clicking on a metal disc in the heating pad, a [[nucleation]] center is formed which causes the solution to crystallize into solid sodium acetate trihydrate again. The bond-forming process of crystallization is [[exothermic]], hence heat is emitted.<ref>{{cite web | publisher = [[Journal of Chemical Education]] | url = http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA3/MAIN/ACETATE/PAGE1.HTM | title = Crystallization of Supersaturated Sodium Acetate}}</ref><ref>[http://www.atmos.washington.edu/2003Q3/101/demonstrations/fake_latentheat_supersaturation.html "Fake" latent heat and supersaturation]</ref><ref>{{cite web | title = How do sodium acetate heat pads work? | publisher = [[HowStuffWorks]] | accessdate = 2007-09-03 | url = http://www.howstuffworks.com/question290.htm}}</ref> The [[latent heat of fusion]] is about 264–289 kJ/kg.<ref>Thermal Energy Storage: Systems and Applications, By Ibrahim Dincer, Marc A. Rosen, p. 155 [http://books.google.com/books?id=EsfcWE5lX40C&q=latent+heat+of+fusion+sodium+acetate#search]</ref>
==Preparation==
Sodium acetate is inexpensive, and is usually purchased from chemical suppliers, instead of being synthesized in the laboratory. It is sometimes produced in a laboratory experiment by the reaction of [[acetic acid]] with [[sodium carbonate]], [[sodium bicarbonate]], or [[sodium hydroxide]]. These reactions produce aqueous sodium acetate, and water. Carbon dioxide is produced in the reaction with sodium carbonate and bicarbonate, and it leaves the reaction vessel as a gas (unless the reaction vessel is pressurized).
:CH<sub>3</sub>–COOH + Na<sup>+</sup>[HCO<sub>3</sub>]<sup>–</sup> → CH<sub>3</sub>–COO<sup>–</sup> Na<sup>+</sup> + H<sub>2</sub>O + CO<sub>2</sup>
This is the well-known "fizzing" reaction between [[baking soda]] and [[vinegar]]. 84 grams of sodium bicarbonate react with 750 ml of 8% vinegar to make 82 g sodium acetate in water. By subsequently boiling off most of the water, one can refine either a concentrated solution of sodium acetate or actual crystals.
==Reactions==
Sodium acetate can be used to form an [[ester]] with an alkyl halide such as [[bromoethane]]:
: H<sub>3</sub>C–COO<sup>–</sup> Na<sup>+</sup> + [[Bromoethane|Br–CH<sub>2</sub>–CH<sub>3</sub>]] → [[Ethyl acetate|H<sub>3</sub>C–COO–CH<sub>2</sub>–CH<sub>3</sub>]] + [[Sodium bromide|NaBr]]
In such a reaction, the sodium acetate is usually complexed with Cesium in order to increase the nucleophilicity of the carboxylate group.
==Gallery==
<gallery>
Image:Hand_warmer.jpg|A [[hand warmer]] containing a supersaturated solution of sodium acetate which releases heat on crystallization
</gallery>
==References==
<references/>
==External links==
*[http://www.amazingrust.com/Experiments/how_to/Hot-Ice.html Hot Ice – Instructions, Pictures, and Videos]
*[http://youtube.com/watch?v=aC-KOYQsIvU&mode=related&search= Video on how to make hot ice using sodium acetate]
*[http://jchemed.chem.wisc.edu/JCeSoft/CCA/CCA3/MAIN/ACETATE/PAGE1.HTM More information, videos, and pictures]
[[Category:Acetates]]
[[Category:Sodium compounds]]
[[Category:Food additives]]
[[ar:خلات صوديوم]]
[[bs:Natrijum acetat]]
[[cs:Octan sodný]]
[[de:Natriumacetat]]
[[es:Acetato de sodio]]
[[fr:Acétate de sodium]]
[[id:Natrium asetat]]
[[it:Acetato di sodio]]
[[he:סודיום אצטט]]
[[hu:Nátrium-acetát]]
[[nl:Natriumacetaat]]
[[ja:酢酸ナトリウム]]
[[pl:Octan sodu]]
[[pt:Acetato de sódio]]
[[ru:Ацетат натрия]]
[[sk:Octan sodný]]
[[fi:Natriumasetaatti]]
[[zh:乙酸钠]]