Sodium acetate, CH₃COONa, also abbreviated Na O Ac, is the

sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...

of acetic acid. This colorless

deliquescent Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substance' ...

salt has a wide range of uses.

Applications

Biotechnological

Sodium acetate is used as the

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...

source for culturing

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...

. Sodium acetate is also useful for increasing yields of DNA isolation by ethanol precipitation.

Industrial

Sodium acetate is used in the

textile Textile is an umbrella term that includes various fiber-based materials, including fibers, yarns, filaments, threads, different fabric types, etc. At first, the word "textiles" only referred to woven fabrics. However, weaving is not the ...

industry to neutralize sulfuric acid waste streams and also as a

photoresist A photoresist (also known simply as a resist) is a light-sensitive material used in several processes, such as photolithography and photoengraving, to form a patterned coating on a surface. This process is crucial in the electronic industry. ...

while using

aniline dyes Aniline is an organic compound with the formula C6 H5 NH2. Consisting of a phenyl group attached to an amino group, aniline is the simplest aromatic amine. It is an industrially significant commodity chemical, as well as a versatile startin ...

. It is also a

pickling Pickling is the process of preserving or extending the shelf life of food by either anaerobic fermentation in brine or immersion in vinegar. The pickling procedure typically affects the food's texture and flavor. The resulting food is cal ...

agent in chrome

tanning Tanning may refer to: *Tanning (leather), treating animal skins to produce leather *Sun tanning, using the sun to darken pale skin **Indoor tanning, the use of artificial light in place of the sun **Sunless tanning, application of a stain or dye t ...

and helps to impede

vulcanization Vulcanization (British: Vulcanisation) is a range of processes for hardening rubbers. The term originally referred exclusively to the treatment of natural rubber with sulfur, which remains the most common practice. It has also grown to includ ...

chloroprene Chloroprene is the common name for 2-chlorobuta-1,3-diene (IUPAC name) with the chemical formula CH2=CCl−CH=CH2. Chloroprene is a colorless volatile liquid, almost exclusively used as a monomer for the production of the polymer polychloroprene ...

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 Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wid ...

sealant Sealant is a substance used to block the passage of fluids through openings in materials, a type of mechanical seal. In building construction ''sealant'' is sometimes synonymous with '' caulking'' and also serve the purposes of blocking dust, so ...

, while also being environmentally benign and cheaper than the commonly used epoxy alternative for sealing concrete against water

permeation In physics and engineering, permeation (also called imbuing) is the penetration of a permeate (a fluid such as a liquid, gas, or vapor) through a solid. It is directly related to the concentration gradient of the permeate, a material's intrins ...

Food

Sodium acetate may be added to food as a seasoning, sometimes in the form of

sodium diacetate Sodium diacetate is a compound with formula . It is a salt of acetic acid. It is a colorless solid that is used in seasonings and as an antimicrobial agent. Preparation and structure The salt forms upon half- neutralization of acetic acid foll ...

, a one-to-one complex of sodium acetate and acetic acid, given the

E-number E numbers ("E" stands for "Europe") are codes for substances used as food additives, including those found naturally in many foods such as vitamin C, for use within the European Union (EU) and European Free Trade Association (EFTA). Commonly f ...

E262. It is often used to give potato chips a

salt and vinegar Vinegar is an aqueous solution of acetic acid and trace compounds that may include flavorings. Vinegar typically contains 5–8% acetic acid by volume. Usually, the acetic acid is produced by a double fermentation, converting simple sugars to ...

flavour, and may be used as a substitute for vinegar itself on potato chips as it doesn't add moisture to the final product. Sodium acetate (anhydrous) is widely used as a shelf-life extending agent, pH control agent It is safe to eat at low concentration.

Buffer solution

A solution of sodium acetate (a basic salt of acetic acid) and acetic acid can act as a

buffer Buffer may refer to: Science * Buffer gas, an inert or nonflammable gas * Buffer solution, a solution used to prevent changes in pH * Buffering agent, the weak acid or base in a buffer solution * Lysis buffer, in cell biology * Metal ion 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

Sodium acetate is also used in

heating pad 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 electri ...

hand warmer Hand warmers are small (mostly disposable) packets which are held in the hand and produce heat on demand to warm cold hands. They are commonly used in outdoor activities. Other types of warmers are available to provide soothing heat for muscular ...

s, and hot ice. Sodium acetate trihydrate crystals melt at ,Courty JM, Kierlik E, Les chaufferettes chimiques, Pour la Science, décembre 2008, pp. 108–110 dissolving in their

water of crystallization In chemistry, water(s) of crystallization or water(s) of hydration are water molecules that are present inside crystals. Water is often incorporated in the formation of crystals from aqueous solutions. In some contexts, water of crystallization i ...

. 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 bond-forming process of crystallization is exothermic. The

latent heat of fusion In thermodynamics, the enthalpy of fusion of a substance, also known as (latent) heat of fusion, is the change in its enthalpy resulting from providing energy, typically heat, to a specific quantity of the substance to change its state from a s ...

is about 264–289 kJ/kg.Ibrahim Dincer and Marc A. Rosen
Thermal Energy Storage: Systems and Applications
page 155 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.

Preparation

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 5–8% solution known as

vinegar Vinegar is an aqueous solution of acetic acid and trace compounds that may include flavorings. Vinegar typically contains 5–8% acetic acid by volume. Usually, the acetic acid is produced by a double fermentation, converting simple sugars to eth ...

, 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 + : → + Industrially, sodium acetate trihydrate is prepared by reacting acetic acid with sodium hydroxide using

water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...

as the

solvent A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...

. :CH₃COOH + NaOH → CH₃COONa + H₂O

Structure

The

crystal structure In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric patterns ...

of anhydrous sodium acetate has been described as alternating sodium-carboxylate and

methyl group In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in ma ...

layers. Sodium acetate

trihydrate In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was underst ...

's structure consists of distorted octahedral coordination at sodium. Adjacent octahedra share edges to form one-dimensional chains.

Hydrogen bonding In chemistry, a hydrogen bond (or H-bond) is a primarily electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to a more electronegative "donor" atom or group (Dn), and another electronegative atom bearing a l ...

in two dimensions between acetate ions and

water of hydration In chemistry, water(s) of crystallization or water(s) of hydration are water molecules that are present inside crystals. Water is often incorporated in the formation of crystals from aqueous solutions. In some contexts, water of crystallization i ...

links the chains into a three-dimensional network.

Reactions

Sodium acetate can be used to form an

ester In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides a ...

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.

References

External links

Hot Ice – Instructions, Pictures, and VideosHow Sodium Acetate heating pads work
* {{Authority control Acetates E-number additives Food additives Organic sodium salts Photographic chemicals