Sodium acetate
From Wikipedia, the free encyclopedia
| Sodium acetate | |
|---|---|
 |
|
| General | |
| Systematic name | sodium acetate (IUPAC) sodium ethanoate (systematic) |
| Other names | Acetic acid sodium salt |
| Molecular formula | CH3CO2Na |
| Molar mass | 82.03 g/mol (anhydrous) 136.08 g/mol (trihydrate) |
| Appearance | White deliquescent powder |
| CAS number | [127-09-3] (anhydrous) [6131-90-4] (trihydrate) |
| Properties | |
| Density and phase | 1.45 g/cm³, solid |
| Solubility in water | 76 g/100 ml (0°C) |
| Melting point | Loses water at 120 °C Decomposes at 324 °C |
| Boiling point | Decomposes |
| Basicity (pKb) | ? |
| Structure | |
| Crystal structure | ? |
| Dipole moment | ? D |
| Hazards | |
| MSDS | External MSDS |
| Main hazards | Irritant |
| NFPA 704 |
1
1
0
|
| Flash point | ?°C |
| R/S statement | R: ? S: ? |
| RTECS number | ? |
| Supplementary data page | |
| Structure and properties |
n, εr, etc. |
| Thermodynamic data |
Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Related compounds | |
| Other anions | sodium formate |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
|
Sodium acetate, (also rarely, sodium ethanoate) is the sodium salt of acetic acid. It is an inexpensive chemical produced in industrial quantities for a wide range of uses. As the conjugate base of acetic acid, it is a relatively strong base.
Contents |
[edit] Applications
Sodium acetate is used in the textile industry to neutralize sulfuric acid waste streams, and as a photoresist while using aniline dyes. It is also a pickling agent in chrome tanning, and it helps to retard vulcanization of chloroprene in synthetic rubber production. Sodium acetate may be added to foods as a preservative; in this application it is usually labelled E262.
As the conjugate base of a weak acid, a solution of sodium acetate can act as a buffer to keep a relatively constant pH. This is useful especially in biochemical applications where reactions are pH dependent.
Sodium acetate is also used in consumer heating pads or hand warmers. When sodium acetate trihydrate crystals are heated to 100 °C, water is driven off to give a supersaturated solution of sodium acetate in water. By clicking on a 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. [1] [2]
[edit] Preparation
Sodium acetate can be prepared in the laboratory easily by the reaction of acetic acid with sodium carbonate, sodium bicarbonate, or sodium hydroxide to name a few bases which contain sodium.
- H3C–COOH + Na+[HCO3]– → H3C–COO– Na+ + H2O + CO2
This is the well-known "fizzing" reaction between baking soda and vinegar. By subsequently boiling off most of the water, one can refine either a concentrated solution of sodium acetate or actual crystals. However (like most reactions) the baking soda and vinegar must be combined in exact proportions to avoid excess acid or bicarbonate in the final product if preparing a solution. For preparing crystals, if there is an excess of acetic acid, the acetic acid would be easily driven off, but not an excess of sodium bicarbonate.
[edit] Reactions
Sodium acetate is a strong base which can neutralize many acids. It can also be used to form an ester with an alkyl halide such as bromoethane:
- H3C–COO– Na+ + Br–CH2–CH3 → H3C–COO–CH2–CH3 + NaBr
[edit] Gallery
 A hand warmer containing a supersaturated solution of sodium acetate which releases heat on crystallization |
