Sodium acetate

Sodium Acetate, with the chemical formula CH₃COONa, is the sodium salt of acetic acid. It appears as a white crystalline powder, odorless or with a mild vinegar-like smell (especially when heated). Sodium acetate is moderately hygroscopic, particularly in its anhydrous form. It is available in two forms: anhydrous and hydrated (commonly the trihydrate form, CH₃COONa·3H₂O).

Structure of Sodium Acetate

Sodium acetate is an ionic compound composed of a sodium cation (Na⁺) and an acetate anion (CH₃COO⁻). The acetate ion consists of a methyl group (CH₃) bonded to a carboxylate group (COO⁻). In the carboxylate group, the double bond between carbon and oxygen exhibits resonance, meaning the negative charge is delocalized over the two oxygen atoms.

Chemical Formula: CH₃COONa
Resonance Structure: O=C–O⁻ ⇄ ⁻O–C=O

Properties of Sodium Acetate

• Appearance: White crystalline powder

• Odor: Odorless; may release a vinegar-like smell when heated

• Solubility: Highly soluble in water; moderately soluble in ethanol (~1.4 g/100 mL)

• Hygroscopicity: Anhydrous form absorbs moisture from the air

• Basic Nature: As the salt of a weak acid and strong base (NaOH), its aqueous solution is slightly alkaline (pH ~8–9 for a 0.1 M solution)

• Melting Point: Anhydrous form decomposes around 324°C; trihydrate melts at ~58°C, releasing water of crystallization

• Buffering Properties: In combination with acetic acid, it forms a buffer solution effective within a pH range of 4 to 6.5

• Chemical Behavior: Can release gases such as acetic acid or CO₂ when in contact with strong acids or oxidizing agents

Applications of Sodium Acetate

Food Industry

• Used as a food additive (E262) for pH regulation, providing a salty/sour taste, and as a preservative

• Acts as an antibacterial and antifungal agent in some food formulations

Pharmaceutical and Medical

• Serves as a sodium source in IV injections or dialysis solutions

• Functions as a buffer component in drug formulations and biological reactions

Textile Industry

• Used in dye baths to control pH and aid in dye uptake

• Neutralizes residual acids like H₂SO₄

• Helps prevent static electricity buildup

Construction Industry

• Acts as an additive to control pH and improve freeze resistance in concrete (e.g., in sealants)

Laboratory Use

• Employed in buffer preparation (especially in biochemistry and DNA extraction)

• Used as a carbon source in bacterial culture media

• Forms part of extraction buffers in molecular biology

Hand Warmers and Heating Pads

• Utilizes supersaturated sodium acetate trihydrate solution that releases latent heat (~264–289 kJ/kg) upon sudden crystallization

Other Uses

• Delays curing in chloroprene rubber production

• Used in leather tanning and dye manufacturing

Advantages of Sodium Acetate

• Generally safe for food use as approved by the FDA in regulated amounts

• Effective buffering capacity

• Highly compatible with industrial processes

• Low cost

• Preservative effect (antimicrobial)

• Useful in phase-change thermal storage systems

Disadvantages of Sodium Acetate

• Moderately hygroscopic (especially in anhydrous form) → requires airtight storage

• Irritant to eyes and skin upon contact

• Dust inhalation may cause respiratory irritation

• Ingestion in high amounts may lead to digestive upset or hypernatremia

• Thermal decomposition at high temperatures may release irritating vapors

• Caution in patients with kidney or heart issues due to electrolyte imbalances

• Pharmaceutical forms may contain aluminum or other excipients; special care is needed in premature infants or patients with renal insufficiency