Sodium acetate

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Sodium acetate
Sodium acetate
Ball-and-stick model of the acetate anionThe sodium cation
Acetate de sodium hydraté.jpg
Identifiers
CAS number127-09-3 YesY, 6131-90-4 (trihydrate)
PubChem517045
ChemSpider29105 YesY
UNIINVG71ZZ7P0 YesY
ChEBICHEBI:32954 YesY
ChEMBLCHEMBL1354 YesY
RTECS numberAJ4300010 (anhydrous)
AJ4580000
ATC codeB05XA08
Jmol-3D imagesImage 1
Properties
Molecular formulaC2H3NaO2
Molar mass82.03 g mol−1
AppearanceWhite deliquescent powder
Odorvinegar
Density1.528 g/cm3
1.45 g/cm3 (trihydrate)
Melting point324 °C (anhydrous)
58 °C (trihydrate)
Boiling point881.4 °C (anhydrous)
122 °C (trihydrate)(decomposes)
Solubility in water36.2 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)
Solubilitysoluble in ethanol (5.3 g/100 mL (trihydrate)
Basicity (pKb)9.25
Refractive index (nD)1.464
Structure
Crystal structuremonoclinic
Hazards
MSDSExternal MSDS
Main hazardsIrritant
NFPA 704
NFPA 704.svg
1
1
0
Flash point250 °C; 482 °F; 523 K
Autoignition temperature607 °C; 1,125 °F; 880 K
Related compounds
Other anionsSodium formate
Sodium propionate
Other cationsPotassium acetate
Calcium acetate
Related compoundsSodium diacetate
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references
 
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Sodium acetate
Sodium acetate
Ball-and-stick model of the acetate anionThe sodium cation
Acetate de sodium hydraté.jpg
Identifiers
CAS number127-09-3 YesY, 6131-90-4 (trihydrate)
PubChem517045
ChemSpider29105 YesY
UNIINVG71ZZ7P0 YesY
ChEBICHEBI:32954 YesY
ChEMBLCHEMBL1354 YesY
RTECS numberAJ4300010 (anhydrous)
AJ4580000
ATC codeB05XA08
Jmol-3D imagesImage 1
Properties
Molecular formulaC2H3NaO2
Molar mass82.03 g mol−1
AppearanceWhite deliquescent powder
Odorvinegar
Density1.528 g/cm3
1.45 g/cm3 (trihydrate)
Melting point324 °C (anhydrous)
58 °C (trihydrate)
Boiling point881.4 °C (anhydrous)
122 °C (trihydrate)(decomposes)
Solubility in water36.2 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)
Solubilitysoluble in ethanol (5.3 g/100 mL (trihydrate)
Basicity (pKb)9.25
Refractive index (nD)1.464
Structure
Crystal structuremonoclinic
Hazards
MSDSExternal MSDS
Main hazardsIrritant
NFPA 704
NFPA 704.svg
1
1
0
Flash point250 °C; 482 °F; 523 K
Autoignition temperature607 °C; 1,125 °F; 880 K
Related compounds
Other anionsSodium formate
Sodium propionate
Other cationsPotassium acetate
Calcium acetate
Related compoundsSodium diacetate
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Sodium acetate, C2H3NaO2, also abbreviated NaOAc,[1] also sodium ethanoate, is the sodium salt of acetic acid. This colourless salt has a wide range of uses.

Applications[edit]

Industrial[edit]

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. In processing cotton for disposable cotton pads, sodium acetate is used to eliminate the buildup of static electricity.

Concrete longevity[edit]

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.[2]

Food[edit]

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,[3] given the E-number E262. A frequent use is to impart a salt and vinegar flavor to potato chips.

Buffer solution[edit]

As the conjugate base of acetic 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 in a mildly acidic range (pH 4-6).

Heating pad[edit]

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 137.12°F / 58.4°C,[4] (to 136.4°F / 58°C [5]) dissolving in their water of crystallization. When they are heated past the melting point 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.[6][7] The latent heat of fusion is about 264–289 kJ/kg.[5] 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.[8]

An inexpensive hand warmer containing a supersaturated solution of sodium acetate which releases heat on crystallization

Preparation[edit]

a crystal of sodium acetate trihydrate (length 1.7 centimetre)

For laboratory use, sodium acetate is very inexpensive, and usually purchased instead of being synthesized. It is sometimes produced in a laboratory experiment by the reaction of variable concentration acetic acid, colloquially known in its 5-8 % solution as vinegar, with sodium carbonate ("washing soda"), sodium bicarbonate ("baking soda"), or sodium hydroxide ("lye"). Any of these reactions produce sodium acetate and water. When a sodium and carbonate ion containing compound is used as a reactant, the carbonate anion is displaced from sodium bicarbonate or sodium carbonate and monatomic hydrogen from the hydroxide in acetic acid, the intermediate carbonic acid is formed. Carbonic acid readily decomposes under normal conditions into gaseous carbon dioxide and water. This is the reaction taking place in the well known "volcano" that occurs when the household products, baking soda and vinegar, are combined.

CH3COOH + NaHCO3 → CH3COONa + H2CO
3
H2CO
3
CO
2
+ H
2
O

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

CH3COOH + NaOH → CH3COONa + H2O

Reactions[edit]

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

CH3COONa + BrCH2CH3CH3COOCH2CH3 + NaBr

Caesium salts catalyze this reaction.

References[edit]

  1. ^ Clayden, Jonathan; Greeves, Nick; Warren, Stuart; Wothers, Peter (2001). Organic Chemistry (1st ed.). Oxford University Press. ISBN 978-0-19-850346-0. 
  2. ^ "Potato Chip Flavoring Boosts Longevity Of Concrete". Science Daily. 8 August 2007. 
  3. ^ Jungbunzlauer - General Information
  4. ^ [Courty JM, Kierlik E, Les chaufferettes chimiques, Pour la Science, décembre 2008, p 108-110]
  5. ^ a b Ibrahim Dincer and Marc A. Rosen. Thermal Energy Storage: Systems and Applications, page 155
  6. ^ "Crystallization of Supersaturated Sodium Acetate". Journal of Chemical Education. 
  7. ^ Fake latent heat and supersaturation
  8. ^ "How do sodium acetate heat pads work?". HowStuffWorks. Retrieved 2007-09-03. 

External links[edit]