Sodium acetate

Last updated
Sodium acetate
Sodium-acetate-2D-skeletal.png
Sodium-acetate-form-I-xtal-sheet-3D-bs-17.png
Octan sodny.JPG
Names
Preferred IUPAC name
Sodium acetate
Systematic IUPAC name
Sodium ethanoate
Other names
Hot ice (sodium acetate trihydrate)
Identifiers
3D model (JSmol)
3595639
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.004.386 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • anhydrous:204-823-8
E number E262 (preservatives)
20502
KEGG
PubChem CID
RTECS number
  • anhydrous:AJ4300010 (anhydrous)
    AJ4580000
UNII
  • InChI=1S/C2H4O2.Na/c1-2(3)4;/h1H3,(H,3,4);/q;+1/p-1 Yes check.svgY
    Key: VMHLLURERBWHNL-UHFFFAOYSA-M Yes check.svgY
  • anhydrous:InChI=1/C2H4O2.Na/c1-2(3)4;/h1H3,(H,3,4);/q;+1/p-1
    Key: VMHLLURERBWHNL-REWHXWOFAT
  • anhydrous:[Na+].[O-]C(=O)C
Properties
C2H3NaO2
Molar mass 82.034 g·mol−1
AppearanceWhite deliquescent powder or 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
1.464
Structure
Monoclinic
Thermochemistry
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]
−709.32 kJ/mol (anhydrous) [4]
−1604 kJ/mol (trihydrate) [2]
−607.7 kJ/mol (anhydrous) [4]
Pharmacology
B05XA08 ( WHO )
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
Irritant
NFPA 704 (fire diamond)
NFPA 704.svgHealth 0: Exposure under fire conditions would offer no hazard beyond that of ordinary combustible material. E.g. sodium chlorideFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazards (white): no code
0
1
1
Flash point >250 °C (482 °F; 523 K) [5]
607 °C (1,125 °F; 880 K) [5]
Lethal dose or concentration (LD, LC):
3530 mg/kg (oral, rat)
>10000 mg/kg (rabbit, dermal)
>30 g/m3 (rat, 1 h)
Safety data sheet (SDS) Fisher Scientific
Related compounds
Other anions
Sodium formate
Sodium propionate
Other cations
Potassium 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).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Sodium acetate, CH3COONa, also abbreviated Na O Ac, [8] is the sodium salt of acetic acid. This salt is colorless deliquescent, and Hygroscopic.

Contents

Applications

Biotechnological

Sodium acetate is used as the carbon source for culturing bacteria. Sodium acetate can also be useful for increasing yields of DNA isolation by ethanol precipitation.

Industrial

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

Concrete longevity

Sodium acetate is used to mitigate water damage to concrete by acting as a concrete sealant, while also being environmentally benign and cheaper than the commonly used epoxy alternative for sealing concrete against water permeation. [9]

Food

Sodium acetate (anhydrous) is widely used as a shelf-life extending agent and pH-control agent. [10] It is safe to eat at low concentration. [11]

Buffer solution

A solution of sodium acetate (a basic salt of acetic acid) and acetic acid can act as a buffer to keep a relatively constant pH level. This is useful especially in biochemical applications where reactions are pH-dependent in a mildly acidic range (pH 4–6).

Heating pad

A hand warmer contains a supersaturated solution of sodium acetate which releases heat upon crystallization Hand warmer.jpg
A hand warmer contains a supersaturated solution of sodium acetate which releases heat upon crystallization

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.

Solubility from CRC Handbook Solubilite NaC2H3O2.png
Solubility from CRC Handbook

Sodium acetate trihydrate crystals melt at 58–58.4 °C (136.4–137.1 °F), [12] [13] dissolving in their water of crystallization [ citation needed ]. 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 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. [14] The latent heat of fusion is about 264–289 kJ/kg. [12] 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. [15]

Preparation

A crystal of sodium acetate trihydrate (length 1.7 centimetres) Sodium acetate trihydrate crystal - 2009-01-28.jpg
A crystal of sodium acetate trihydrate (length 1.7 centimetres)

For laboratory use, sodium acetate is inexpensive and usually purchased instead of being synthesized. It is sometimes produced in a laboratory experiment by the reaction of acetic acid, commonly in the 5–18% solution known as vinegar, with sodium carbonate ("washing soda"), sodium bicarbonate ("baking soda"), or sodium hydroxide ("lye", or "caustic soda"). Any of these reactions produce sodium acetate and water. When a sodium and carbonate ion-containing compound is used as the reactant, the carbonate anion from sodium bicarbonate or carbonate, reacts with the hydrogen from the carboxyl group (-COOH) in acetic acid, forming carbonic acid. 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
2O

Industrially, sodium acetate trihydrate is prepared by reacting acetic acid with sodium hydroxide using water as the solvent.

CH3COOH + NaOH → CH3COONa + H2O.

To manufacture anhydrous sodium acetate industrially, the Niacet Process is used. Sodium metal ingots are extruded through a die to form a ribbon of sodium metal, usually under an inert gas atmosphere such as N2 then immersed in anhydrous acetic acid.

2 CH3COOH + 2 Na →2 CH3COONa + H2.

The hydrogen gas is normally a valuable byproduct.

Structure

The crystal structure of anhydrous sodium acetate has been described as alternating sodium-carboxylate and methyl group layers. [16] 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. [17] [18]

Comparison of anhydrous and trihydrate crystal structures
Degree of hydrationAnhydrous [16] Trihydrate [17] [18]
Na coordination Sodium-acetate-form-I-xtal-coordination-at-Na2-3D-bs-17.png Sodium-acetate-trihydrate-xtal-Na-coordination-3D-bs-17.png
Strongly bonded aggregation Sodium-acetate-form-I-xtal-sheet-3D-sf.png
2D sheet		 Sodium-acetate-trihydrate-chain-from-xtal-3D-bs-17.png
1D chain
Weakly bonded aggregation Sodium-acetate-form-I-xtal-packing-c-3D-bs-17.png
sheets stacked with
hydrophobic surfaces in contact		 Sodium-acetate-trihydrate-chain-packing-and-hydrogen-bonding-in-xtal-3D-bs-17.png
chains linked by hydrogen bonds
(one chain highlighted in light blue)

Reactions

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

CH3COONa + BrCH2CH3 → CH3COOCH2CH3 + NaBr

Sodium acetate undergoes decarboxylation to form methane (CH4) under forcing conditions (pyrolysis in the presence of sodium hydroxide):

CH3COONa + NaOH → CH4 + Na2CO3

Calcium oxide is the typical catalyst used for this reaction. Cesium salts also catalyze this reaction.[ citation needed ]

Related Research Articles

<span class="mw-page-title-main">Salt (chemistry)</span> Chemical compound involving ionic bonding

In chemistry, a salt or ionic compound is a chemical compound consisting of an assembly of positively charged ions (cations) and negatively charged ions (anions), which results in a compound with no net electric charge. The constituent ions are held together by electrostatic forces termed ionic bonds.

<span class="mw-page-title-main">Sodium hydroxide</span> Chemical compound with formula NaOH

Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations Na+ and hydroxide anions OH−.

<span class="mw-page-title-main">Sodium bicarbonate</span> Chemical compound

Sodium bicarbonate (IUPAC name: sodium hydrogencarbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation (Na+) and a bicarbonate anion (HCO3−). Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder. It has a slightly salty, alkaline taste resembling that of washing soda (sodium carbonate). The natural mineral form is nahcolite, although it is more commonly found as a component of the mineral trona.

<span class="mw-page-title-main">Sodium carbonate</span> Chemical compound

Sodium carbonate is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, odourless, water-soluble salts that yield alkaline solutions in water. Historically, it was extracted from the ashes of plants grown in sodium-rich soils, and because the ashes of these sodium-rich plants were noticeably different from ashes of wood, sodium carbonate became known as "soda ash". It is produced in large quantities from sodium chloride and limestone by the Solvay process, as well as by carbonating sodium hydroxide which is made using the chloralkali process.

<span class="mw-page-title-main">Acetate</span> Salt compound formed from acetic acid and a base

An acetate is a salt formed by the combination of acetic acid with a base. "Acetate" also describes the conjugate base or ion typically found in aqueous solution and written with the chemical formula C
2H
3O−
2. The neutral molecules formed by the combination of the acetate ion and a positive ion are also commonly called "acetates". The simplest of these is hydrogen acetate with corresponding salts, esters, and the polyatomic anion CH
3CO−
2, or CH
3COO−
.

<span class="mw-page-title-main">Magnesium carbonate</span> Chemical compound

Magnesium carbonate, MgCO3, is an inorganic salt that is a colourless or white solid. Several hydrated and basic forms of magnesium carbonate also exist as minerals.

<span class="mw-page-title-main">Sodium sulfate</span> Chemical compound with formula Na2SO4

Sodium sulfate (also known as sodium sulphate or sulfate of soda) is the inorganic compound with formula Na2SO4 as well as several related hydrates. All forms are white solids that are highly soluble in water. With an annual production of 6 million tonnes, the decahydrate is a major commodity chemical product. It is mainly used as a filler in the manufacture of powdered home laundry detergents and in the Kraft process of paper pulping for making highly alkaline sulfides.

<span class="mw-page-title-main">Barium chloride</span> Chemical compound

Barium chloride is an inorganic compound with the formula BaCl2. It is one of the most common water-soluble salts of barium. Like most other water-soluble barium salts, it is a white powder, highly toxic, and imparts a yellow-green coloration to a flame. It is also hygroscopic, converting to the dihydrate BaCl2·2H2O, which are colourless crystals with a bitter salty taste. It has limited use in the laboratory and industry.

A heating pad is a pad used for warming of parts of the body in order to manage pain. Localized application of heat causes the blood vessels in that area to dilate, enhancing perfusion to the targeted tissue. Types of heating pads include electrical, chemical and hot water bottles.

Sodium perborate is chemical compound whose chemical formula may be written NaH2BO4, Na2H4B2O8, or, more properly, [Na+]2[B2O4(OH)4]2−. Its name is sometimes abbreviated as PBS.

<span class="mw-page-title-main">Uranyl chloride</span> Chemical compound

Uranyl chloride refers to inorganic compounds with the formula UO2Cl2(H2O)n where n = 0, 1, or 3. These are yellow-colored salts.

<span class="mw-page-title-main">Potassium acetate</span> Colourless soluble salt of acetic acid

Potassium acetate (also called potassium ethanoate), (CH3COOK) is the potassium salt of acetic acid. It is a hygroscopic solid at room temperature.

<span class="mw-page-title-main">Sodium formate</span> Chemical compound

Sodium formate, HCOONa, is the sodium salt of formic acid, HCOOH. It usually appears as a white deliquescent powder.

<span class="mw-page-title-main">Cobalt(II) acetate</span> Chemical compound

Cobalt(II) acetate is the cobalt salt of acetic acid. It is commonly found as the tetrahydrate Co(CH3CO2)2·4 H2O, abbreviated Co(OAc)2·4 H2O. It is used as a catalyst.

<span class="mw-page-title-main">Magnesium acetate</span> Chemical compound

Anhydrous magnesium acetate has the chemical formula Mg(C2H3O2)2 and in its hydrated form, magnesium acetate tetrahydrate, it has the chemical formula Mg(CH3COO)2 • 4H2O. In this compound magnesium has an oxidation state of 2+. Magnesium acetate is the magnesium salt of acetic acid. It is deliquescent and upon heating, it decomposes to form magnesium oxide. Magnesium acetate is commonly used as a source of magnesium in biological reactions.

<span class="mw-page-title-main">Barium acetate</span> Chemical compound

Barium acetate (Ba(C2H3O2)2) is the salt of barium(II) and acetic acid. Barium acetate is toxic to humans, but it has use in chemistry and manufacturing.

<span class="mw-page-title-main">Thorium(IV) nitrate</span> Chemical compound

Thorium(IV) nitrate is a chemical compound, a salt of thorium and nitric acid with the formula Th(NO3)4. A white solid in its anhydrous form, it can form tetra- and pentahydrates. As a salt of thorium it is weakly radioactive.

<span class="mw-page-title-main">Cerium(IV) hydroxide</span> Chemical compound

Cerium(IV) hydroxide, also known as ceric hydroxide, is an inorganic compound with the chemical formula Ce(OH)4. It is a yellowish powder that is insoluble in water but soluble in concentrated acids.

<span class="mw-page-title-main">Europium(III) acetate</span> Chemical compound

Europium(III) acetate is an inorganic salt of europium and acetic acid with the chemical formula of Eu(CH3COO)3. In this compound, europium exhibits the +3 oxidation state. It can exist in the anhydrous form, sesquihydrate and tetrahydrate. Its hydrate molecule is a dimer.

Tin(IV) acetate is the acetate salt of tin(IV), with the chemical formula of Sn(CH3COO)4.

References

  1. ↑ "Sodium Acetate". International Chemical Safety Cards. National Institute of Occupational Safety and Health. 2018-09-18.
  2. 1 2 3 "sodium acetate trihydrate". chemister.ru.
  3. ↑ Seidell, Atherton; Linke, William F. (1952). Solubilities of Inorganic and Organic Compounds. Van Nostrand.
  4. 1 2 3 4 5 6 "sodium acetate". chemister.ru.
  5. 1 2 3 Sigma-Aldrich Co., Sodium acetate. Retrieved on 2014-06-07.
  6. 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).
  7. ↑ 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).
  8. ↑ Clayden, Jonathan; Greeves, Nick; Warren, Stuart; Wothers, Peter (2001). Organic Chemistry (1st ed.). Oxford University Press. ISBN   978-0-19-850346-0.
  9. ↑ "Potato Chip Flavoring Boosts Longevity Of Concrete". Science Daily . 8 August 2007.
  10. ↑ "Food Additive "Sodium Acetate (Anhydrous)"". Mitsubishi Chemical Corporation. Retrieved 16 September 2020.
  11. ↑ 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.
  12. 1 2 Ibrahim Dincer and Marc A. Rosen. Thermal Energy Storage: Systems and Applications, page 155.
  13. ↑ Courty J.-M., Kierlik É. (2008-12-01). "Les chaufferettes chimiques". Pour la Science (in French). pp. 108–110.
  14. ↑ "Crystallization of Supersaturated Sodium Acetate". Journal of Chemical Education. 2015-07-19.
  15. ↑ "How do sodium acetate heat pads work?". HowStuffWorks. April 2000. Retrieved 2007-09-03.
  16. 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.
  17. 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.
  18. 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.
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