Misplaced Pages

This is an old revision of this page, as edited by ClueBot NG (talk | contribs) at 16:00, 8 February 2012 (Reverting possible vandalism by 206.82.17.174 to version by 130.207.65.197. False positive? Report it. Thanks, ClueBot NG. (870944) (Bot)). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

Sodium acetate

Names
IUPAC name Sodium acetate
Systematic IUPAC name Sodium ethanoate
Other names Hot ice (Sodium acetate trihydrate)
Identifiers
CAS Number	127-09-3 6131-90-4 (trihydrate)
3D model (JSmol)	Interactive image
ChEBI	CHEBI:32954
ChEMBL	ChEMBL1354
ChemSpider	29105
ECHA InfoCard	100.004.386
E number	E262 (preservatives)
PubChem CID	517045
RTECS number	AJ4300010 (anhydrous) AJ4580000
UNII	NVG71ZZ7P0
CompTox Dashboard (EPA)	DTXSID2027044
InChI InChI=1S/C2H4O2.Na/c1-2(3)4;/h1H3,(H,3,4);/q;+1/p-1Key: VMHLLURERBWHNL-UHFFFAOYSA-M InChI=1/C2H4O2.Na/c1-2(3)4;/h1H3,(H,3,4);/q;+1/p-1Key: VMHLLURERBWHNL-REWHXWOFAT
SMILES .C(=O)C
Properties
Chemical formula	C2H3NaO2
Molar mass	82.0343 g/mol (anhydrous) 136.0799 g/mol (trihydrate)
Appearance	White deliquescent powder odorless
Density	1.528 g/cm 1.45 g/cm (trihydrate)
Melting point	324 °C (anhydrous) 58 °C (trihydrate)
Boiling point	881.4 °C (anhydrous) 122 °C (trihydrate)(decomposes)
Solubility in water	36.2 g/100 ml (0°C) 46.4 g/100 mL (20°C) 139 g/100 mL (60°C) 170.15 g/100 mL (100°C)
Solubility	soluble in ethanol (5.3 g/100 mL (trihydrate)
Basicity (pKb)	9.25
Refractive index (nD)	1.464
Structure
Crystal structure	monoclinic
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Irritant
NFPA 704 (fire diamond)	1 1 0
Flash point	250 °C
Related compounds
Other anions	Sodium formate Sodium propionate
Other cations	Potassium acetate Calcium acetate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). Y verify (what is  ?) Infobox references

Sodium acetate, CH₃COONa, also abbreviated NaOAc, also sodium ethanoate, is the sodium salt of acetic acid. This colourless salt has a wide range of uses.

Applications

Industrial

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.

Concrete longevity

Sodium acetate is used to reduce the damage water can potentially do to concrete by acting as a Concrete sealant, while also being environmentally benign and cheaper than the epoxy alternative that is usually employed for sealing concrete against water permeation .

Food

Sodium acetate may be added to foods as a seasoning. It may be used in the form of sodium diacetate — a 1:1 complex of sodium acetate and acetic acid, given the E-number E262. A frequent use of this form is in salt and vinegar chips in the United States. Many US brands, including national manufacturer Frito-Lay, sell "salt and vinegar flavoured" chips that use this chemical, with lactose and smaller percentages of other chemicals, in lieu of a real salt and vinegar preparation.

Buffer solution

As the conjugate base of a weak acid, a solution of sodium acetate and acetic acid can act as a buffer to keep a relatively constant pH. This is useful especially in biochemical applications where reactions are pH dependent.

Heating pad

Sodium acetate is also used in consumer heating pads or hand warmers and is also used in hot ice. Sodium acetate trihydrate crystals melt at 54°C, (to 58°C ) dissolving in their water of crystallization. When they are heated to around 100°C, and subsequently allowed to cool, the aqueous solution becomes supersaturated. This solution is capable of cooling to room temperature without forming crystals. By clicking on a metal disc in the heating pad, a nucleation centre is formed which causes the solution to crystallize into solid sodium acetate trihydrate again. The bond-forming process of crystallization is exothermic. The latent heat of fusion is about 264–289 kJ/kg. Unlike some other types of heat packs that depend on irreversible chemical reactions, sodium acetate heat packs can be easily recharged by placing in boiling water for a few minutes until all crystals are dissolved; they can be reused many times.

Preparation

For laboratory use, sodium acetate is very inexpensive, and is usually purchased instead of being synthesized. It is sometimes produced in a laboratory experiment by the reaction of acetic acid (also called ethanoic 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). This is the well-known "volcano" reaction between baking soda and vinegar.

CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂

Industrially, sodium acetate is prepared from glacial acetic acid and sodium hydroxide.

CH₃COOH + NaOH → CH₃COONa + H₂O

Reactions

Sodium acetate can be used to form an ester with an alkyl halide such as bromoethane:

CH₃COONa + BrCH₂CH₃ → CH₃COOCH₂CH₃ + NaBr

Caesium salts catalyze this reaction.

References

1. Clayden, Jonathan; Greeves, Nick; Warren, Stuart; Wothers, Peter (2001). Organic Chemistry (1st ed.). Oxford University Press. ISBN 978-0-19-850346-0.
2. http://www.sciencedaily.com/releases/2007/08/070806101941.htm
3. http://www.jungbunzlauer.com/products-applications/products/specialties/sodium-diacetate/general-information.html
4. http://www.fritolay.com/our-snacks/lays-salt-vinegar.html
6. ^ Ibrahim Dincer and Marc A. Rosen. Thermal Energy Storage: Systems and Applications, page 155
7. "Crystallization of Supersaturated Sodium Acetate". Journal of Chemical Education.
8. Fake latent heat and supersaturation
9. "How do sodium acetate heat pads work?". HowStuffWorks. Retrieved 2007-09-03.

External links

• Hot Ice – Instructions, Pictures, and Videos
• Sodium Acetate Experiment yields instant crystals

• Acetates
• Sodium compounds
• Food additives
• Photographic chemicals