Sodium Acetate
Properties
| State | Solid at room temperature |
| Color | White crystalline powder |
| Solubility | Very soluble in water (46.5 g/100 mL at 20 °C) |
| Melting Point | 324 °C (anhydrous); 58 °C (trihydrate) |
| Boiling Point | Decomposes above 324 °C |
About Sodium Acetate
Sodium acetate is the conjugate-base salt of acetic acid, with a molar mass of 82.034 g/mol for the anhydrous form and 136.08 g/mol for the trihydrate that almost everyone actually buys. The trihydrate (CH3COONa·3H2O) is the form that does the famous hot-ice trick: it melts in its own water of crystallization at 58 °C, supercools easily down to room temperature, and snaps back to solid when nudged with a seed crystal — releasing the 264 J/g latent heat of fusion that makes click-pad hand warmers warm. In a biochemistry lab, sodium acetate buffer at pH 4.5–5.5 is one of the most used systems on the bench: it is what RNA precipitations, agarose gel running buffers, and most enzyme assays in that pH window run on. The acetate-acetic acid pair has a pKa of 4.76, so a 50:50 mole ratio holds you right at that sweet spot. In food, E262 sodium diacetate is the salt-and-vinegar flavor on chips and the mold inhibitor in commercial bread.
Where you'll encounter it
If you've ever cracked the metal disc on a chemical hand warmer and watched a clear gel turn into a solid white block in seconds while it warms your fingers, that's supercooled sodium acetate trihydrate releasing crystallization energy. In a molecular biology lab, you reach for the 3 M sodium acetate pH 5.2 stock when precipitating DNA or RNA with ethanol — the acetate neutralizes phosphate backbone charge so the nucleic acid drops out cleanly. Brewers and dyers use sodium acetate as a buffer in mordant baths because it holds pH while metal salts like alum bind to fiber. In leather tanning, acetate buffers control the pH window where chromium tanning crosslinks collagen without precipitating Cr(OH)3. The salt-and-vinegar potato chips you buy are sprayed with a sodium-diacetate-and-malic-acid blend after frying — straight vinegar would make them soggy.
Common Uses
- Buffer component (pH 3.7–5.8) for RNA, DNA, and protein biochemistry
- Latent-heat storage medium in reusable click hand warmers and heating pads
- Salt-and-vinegar flavoring (E262) on chips, bread mold inhibitor
- Mordant fixative in textile dyeing of cotton and silk
- Acetate ion source for nucleic acid ethanol precipitation at pH 5.2
- Concrete sealer to neutralize alkaline efflorescence in restoration
- Pickling agent in sausage and processed meat manufacturing
- Heating-pad solute in supersaturation classroom demonstrations
Safety Information
Low hazard. GHS: not classified — neither H-codes nor P-codes assigned for the pure substance. Generally Recognized as Safe (GRAS) by FDA under 21 CFR 184.1721 with no upper food limit. OSHA has not set a PEL. Dust may cause mild mechanical irritation to eyes and respiratory tract. The trihydrate hot-ice form releases up to 58 °C heat on crystallization — enough for a thermal burn if a hand warmer ruptures against bare skin. Skin contact with concentrated solutions can dry hands over time but does not produce chemical burns. Standard lab PPE (gloves, safety glasses) is sufficient.
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals.