Sodium acetate
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| Names | |
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| Preferred IUPAC name
Sodium acetate | |
| Systematic IUPAC name
Sodium ethanoate | |
| Other names
Hot ice (sodium acetate trihydrate) | |
| Identifiers | |
3D model (JSmol) |
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| Abbreviations | AcONa NaOAc |
| 3595639 | |
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| DrugBank |
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| ECHA InfoCard | 100.004.386 |
| EC Number |
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| E number | E262 (preservatives) |
| 20502 | |
| KEGG |
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PubChem CID |
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CompTox Dashboard (EPA) |
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| Properties | |
| C2H3NaO2 | |
| Molar mass | 82.034 g·mol−1 |
| Appearance | White deliquescent powder or colorless crystals |
| Odor | Vinegar (acetic acid) odor when heated to decomposition[1] |
| Density | 1.528 g/cm3 (20 °C, anhydrous) 1.45 g/cm3 (20 °C, trihydrate)[2] |
| Melting point | 324 °C (615 °F; 597 K) (anhydrous) 58 °C (136 °F; 331 K) (trihydrate) |
| Boiling point | 881.4 °C (1,618.5 °F; 1,154.5 K) (anhydrous) 122 °C (252 °F; 395 K) (trihydrate) decomposes |
| Anhydrous: 119 g/100 mL (0 °C) 123.3 g/100 mL (20 °C) 125.5 g/100 mL (30 °C) 137.2 g/100 mL (60 °C) 162.9 g/100 mL (100 °C) Trihydrate: 32.9 g/100 mL (-10 °C) 36.2 g/100 mL (0 °C) 46.4 g/100 mL (20 °C) 82 g/100 mL (50 °C)[3] | |
| Solubility | Soluble in alcohol, hydrazine, SO2[4] |
| Solubility in methanol | 16 g/100 g (15 °C) 16.55 g/100 g (67.7 °C)[4] |
| Solubility in ethanol | Trihydrate: 5.3 g/100 mL |
| Solubility in acetone | 0.5 g/kg (15 °C)[4] |
| Acidity (pKa) | 24 (20 °C)[4] 4.75 (when mixed with CH3COOH as a buffer)[5] |
| Basicity (pKb) | 9.25 |
| −37.6·10−6 cm3/mol | |
Refractive index (nD) |
1.464 |
| Structure | |
| Monoclinic | |
| Thermochemistry | |
Heat capacity (C) |
100.83 J/(mol·K) (anhydrous)[6] 229 J/(mol·K) (trihydrate)[7] |
Std molar entropy (S⦵298) |
138.1 J/(mol·K) (anhydrous)[6] 262 J/(mol·K) (trihydrate)[2] |
Std enthalpy of formation (ΔfH⦵298) |
−709.32 kJ/mol (anhydrous)[4] −1604 kJ/mol (trihydrate)[2] |
Gibbs free energy (ΔfG⦵) |
−607.7 kJ/mol (anhydrous)[4] |
| Pharmacology | |
| B05XA08 (WHO) | |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards |
Irritant |
| NFPA 704 (fire diamond) | |
| Flash point | >250 °C (482 °F; 523 K)[5] |
| 607 °C (1,125 °F; 880 K)[5] | |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) |
3530 mg/kg (oral, rat) >10000 mg/kg (rabbit, dermal) |
LC50 (median concentration) |
>30 g/m3 (rat, 1 h) |
| Safety data sheet (SDS) | Fisher Scientific |
| Related compounds | |
Other anions |
Sodium formate Sodium propionate Sodium butyrate |
Other cations |
Lithium acetate Potassium acetate Rubidium acetate Cesium acetate Calcium acetate |
Related compounds |
Sodium diacetate |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Sodium acetate is a chemical compound with formula CH3COONa, also abbreviated NaOAc.[8] It is the sodium salt of acetic acid. This salt is colorless, deliquescent, and hygroscopic.[9]
Applications
[edit]Biochemistry and biotechnology
[edit]Buffer solutions composed of sodium acetate and acetic acid are routinely used to maintain pH in a mildly acidic range (pH 4–6). It is also used as a carbon source for culturing bacteria and industrial waste treatment.[10] Sodium acetate can also be useful for increasing yields of DNA isolation by ethanol precipitation.
Industrial
[edit]Sodium acetate is used in the textile industry to neutralize sulfuric acid waste streams and also as a photoresist while using aniline dyes. It is also a pickling agent in chrome tanning and helps to impede vulcanization of chloroprene in synthetic rubber production. It is also used to reduce static electricity during production of disposable cotton pads.[citation needed]
Food
[edit]Anhydrous sodium acetate is widely used as a shelf-life extending agent and pH control agent.[11] It is safe to eat at low concentration.[12]
Heating pad
[edit]
Sodium acetate is also used in heating pads, hand warmers, and "hot ice". A supersaturated solution of sodium acetate in water is supplied with a device to initiate crystallization, a process that releases substantial heat.
Sodium acetate trihydrate crystals melt at 58–58.4 °C (136.4–137.1 °F),[13][14] and the liquid sodium acetate dissolves in the released water of crystallization. When 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 pressing on a metal disc within the heating pad, a nucleation center is formed, causing the solution to crystallize back into solid sodium acetate trihydrate. The process of crystallization is exothermic.[15] The latent heat of fusion is about 264–289 kJ/kg.[13] Unlike some types of heat packs, such as those dependent upon irreversible chemical reactions, a sodium acetate heat pack can be easily reused by immersing the pack in boiling water for a few minutes, until the crystals are completely dissolved, and allowing the pack to slowly cool to room temperature.[16]
Preparation
[edit]Hydrated sodium acetate is produced commercially by treating acetic acid with aqueous sodium hydroxide.[17]
- CH3CO2H + NaOH → CH3CO2Na + H2O
Structure
[edit]The crystal structure of anhydrous sodium acetate has been described as alternating sodium-carboxylate and methyl group layers.[18] Sodium acetate trihydrate's structure consists of distorted octahedral coordination at sodium. Adjacent octahedra share edges to form one-dimensional chains. Hydrogen bonding in two dimensions between acetate ions and water of hydration links the chains into a three-dimensional network.[19][20]
| Degree of hydration | Anhydrous[18] | Trihydrate[19][20] |
|---|---|---|
| Na coordination |  |
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| Strongly bonded aggregation |  2D sheet |
 1D chain |
| Weakly bonded aggregation |  sheets stacked with hydrophobic surfaces in contact |
 chains linked by hydrogen bonds (one chain highlighted in light blue) |
Reactions
[edit]Sodium acetate can be alkylated to form esters. For example, treatment with bromoethane gives ethyl acetate:
- CH3CO2Na + BrC2H5 → CH3CO2C2H5 + NaBr
Sodium acetate undergoes decarboxylation to form methane and carbon dioxide.[21]
References
[edit]- ↑ "Sodium Acetate". International Chemical Safety Cards. National Institute of Occupational Safety and Health. 2018-09-18.
- 1 2 3 "sodium acetate trihydrate". chemister.ru.
- ↑ Seidell, Atherton; Linke, William F. (1952). Solubilities of Inorganic and Organic Compounds. Van Nostrand.
- 1 2 3 4 5 6 "sodium acetate". chemister.ru.
- 1 2 3 Sigma-Aldrich Co., Sodium acetate. Retrieved on 2014-06-07.
- 1 2 Acetic acid, sodium salt in Linstrom, Peter J.; Mallard, William G. (eds.); NIST Chemistry WebBook, NIST Standard Reference Database Number 69, National Institute of Standards and Technology, Gaithersburg (MD) (retrieved 2014-05-25).
- ↑ Acetic acid, sodium salt, hydrate (1:1:3) in Linstrom, Peter J.; Mallard, William G. (eds.); NIST Chemistry WebBook, NIST Standard Reference Database Number 69, National Institute of Standards and Technology, Gaithersburg (MD) (retrieved 2014-05-25).
- ↑ Clayden, Jonathan; Greeves, Nick; Warren, Stuart; Wothers, Peter (2001). Organic Chemistry (1st ed.). Oxford University Press. ISBN 978-0-19-850346-0.
- ↑ "Sodium Acetate: Sodium Acetate, Anhydrous", ACS Reagent Chemicals, Washington, DC: American Chemical Society, January 2017, doi:10.1021/acsreagents.4326, ISBN 978-0-8412-3046-0, retrieved 2025-10-30
- ↑ Fu, Xinrong; Hou, Rongrong; Yang, Peng; Qian, Shengtao; Feng, Zhuqing; Chen, Zhongbing; Wang, Fei; Yuan, Rongfang; Chen, Huilun; Zhou, Beihai (2022). "Application of external carbon source in heterotrophic denitrification of domestic sewage: A review". Science of the Total Environment. 817 153061. doi:10.1016/j.scitotenv.2022.153061. PMID 35026271.
- ↑ "Food Additive "Sodium Acetate (Anhydrous)"". Mitsubishi Chemical Corporation. Retrieved 16 September 2020.
- ↑ Mohammadzadeh-Aghdash, Hossein; Sohrabi, Yousef; Mohammadi, Ali; Shanehbandi, Dariush; Dehghan, Parvin; Ezzati Nazhad Dolatabadi, Jafar (15 August 2018). "Safety assessment of sodium acetate, sodium diacetate and potassium sorbate food additives". Food Chemistry. 257: 211–215. doi:10.1016/j.foodchem.2018.03.020. ISSN 0308-8146. PMID 29622200. S2CID 4596295. Retrieved 16 September 2020.
- 1 2 Ibrahim Dincer and Marc A. Rosen. Thermal Energy Storage: Systems and Applications, page 155.
- ↑ Courty J.-M., Kierlik É. (2008-12-01). "Les chaufferettes chimiques". Pour la Science (in French). pp. 108–110.
- ↑ Pergler, Joseph A.; Ragsdale, Ronald O.; Richmond, Thomas G. (1995). "Crystallization of Supersaturated Sodium Acetate and the Temperature Dependence of the Autoionization Constant of Water". Journal of Chemical Education. 72 (11): 1027. doi:10.1021/ed072p1027.
- ↑ "How do sodium acetate heat pads work?". HowStuffWorks. April 2000. Retrieved 2007-09-03.
- ↑ Le Berre, Carole; Serp, Philippe; Kalck, Philippe; Torrence, G. Paull (2014). "Acetic Acid". Ullmann's Encyclopedia of Industrial Chemistry. pp. 1–34. doi:10.1002/14356007.a01_045.pub3. ISBN 978-3-527-30385-4.
- 1 2 Hsu, Leh-Yeh; Nordman, C. E. (1983). "Structures of two forms of sodium acetate, Na+.C2H3O2−". Acta Crystallogr. C. 39 (6): 690–694. Bibcode:1983AcCrC..39..690H. doi:10.1107/S0108270183005946.
- 1 2 Cameron, T. S.; Mannan, K. M.; Rahman, M. O. (1976). "The crystal structure of sodium acetate trihydrate". Acta Crystallogr. B. 32 (1): 87–90. Bibcode:1976AcCrB..32...87C. doi:10.1107/S0567740876002367.
- 1 2 Wei, K.-T.; Ward, D. L. (1977). "Sodium acetate trihydrate: a redetermination". Acta Crystallogr. B. 33 (2): 522–526. Bibcode:1977AcCrB..33..522W. doi:10.1107/S0567740877003975.
- ↑ Palmer, Donald A.; Drummond, S.E (1986). "Thermal decarboxylation of acetate. Part I. The kinetics and mechanism of reaction in aqueous solution". Geochimica et Cosmochimica Acta. 50 (5): 813–823. doi:10.1016/0016-7037(86)90357-1.
External links
[edit]
- Hot Ice – Instructions, Pictures, and Videos
- How Sodium Acetate heating pads work
- Lavars, Nick (2021-09-15). "Sodium acetate acts as a potential fountain of youth for aging bones". New Atlas. Retrieved 2021-09-16.
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