Sodium Acetate Trihydrate
Sodium acetate trihydrate, also known as sodium ethanoate is an odourless, white crystalline salt which is easily soluble in water. It is made from ethanoic acid and sodium carbonate or sodium hydroxide. It has many applications and is commonly used in the textile industries.
Properties & Specification
- Synonyms.: Acetic acid sodium salt; sodium ethanoate;
- CAS No.: 6131–90–4
- EINECS: 204–823–8
- Formula:CH3COONa 3H2O
- Purity: 98% min
- Mol weight: 136.8
- Density: 1.45
- Melting point: 58C
- Boiling point: >200C
- Autoignition temperature: 607C
- Water solubility: 762 g/L (20 C)
- Appearance:: White crystalline solid
- pH: 8.9 (0.1M at 25C)
Easily soluble in cold water, hot water. Soluble in diethyl ether. Solubility in water: 1 g dissolves in 0.8 ml water 0.6 boiling. Solubility in water: 76.2 g/100 ml @ 0 deg. C; 138.8 g/ 100 ml @ 50 deg. C Solubililty in alcohol: 1 g dissolves in 19 ml alcohol. Solubility in alcohol: 2.1 g/100 ml alcohol @ 18 deg. C
Uses of sodium acetate trihydrate
- Used in hand warmers and heating pads
- Used for making Hot Ice in Heating Pads (Details below for making and link to Video.)
- Used as a Buffer to maintain constant pH in solutions
- Used in Textile industry to neutralise acid wastestreams
- Used in optical lithography and photoengraving
- In the production of synthetic rubber. It helps to retard vulcanization of chloroprene.
- As a pickling agent in Chrome tanning of animal skins in conjunction with chromium sulphate.
- As a concrete sealant
Sodium acetate in the laboratory
In the lab, as the conjugate base of a weak 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. A formulation with ethanol may be used for precipitation of nucleic acids. It is often used in the preparation of gel stains for protein gel electrophoresis.
Details on Making Hot Ice:
Sodium acetate is also used in consumer heating pads or hand warmers and is also used in “hot ice”. When sodium acetate trihydrate crystals (melting point 58 oC) are heated to around 100 oC, they melt. When this melt cools, it gives a supersaturated solution of sodium acetate in water. This solution is capable of supercooling to room temperature, well below its melting point, without forming crystals. By clicking on a metal disc in the heating pad, a nucleation center is formed which causes the solution to crystallize into solid sodium acetate trihydrate again. The bond-forming process of crystallization is exothermic, hence heat is emitted.
Health & safety
Not a hazardous substance or mixture according to Regulation (EC) No 1272/2008 This substance is not classified as dangerous according to Directive 67/548/EEC.