Sodium acetate

• Natriumethanoat ( IUPAC )
• E 262

White crystalline salt

Fixed

1.52 g · cm -3 ( 20 ° C, anhydrous) 1.42 g · cm -3 (20 ° C, trihydrate)

Decomposition at 324 ° C 58 ° C (trihydrate ) by dissolution in their own water of crystallization; Melting point of the pure substance at 300 ° C

Well in water ( 365 g · l-1 at 20 ° C)

-708.8 KJ / mol

Template: Infobox chemical / molecular formula search available

Sodium acetate is a colorless, smelling faintly of vinegar salt. It is the sodium salt of acetic acid and produced for example by the reaction of sodium hydroxide, sodium carbonate or sodium bicarbonate with acetic acid. Occasionally, sodium acetate is NaAc or abbreviated NaOAc, which can lead to confusion, since Ac is the symbol for the element actinium.

Properties

From aqueous solutions crystallized sodium acetate with 3 moles of water of crystallization: Na ( CH3COO ) 3 · H2O. This trihydrate forms large, colorless crystals, and is readily soluble in water (612 g / l at 20 ° C) and dissolves from 58 ° C in its own water of crystallization. At a higher temperature (~ 120 ° C), the crystal water evaporates and creates crystal of anhydrous sodium Na ( CH3COO ), sometimes NaAc ( spelling inorganic chemistry ), written " organically correct" NaOAc. The anhydrous salt is also colorless, flammable, and attracts humidity, it is hygroscopic and readily soluble in water (365 g / l at 20 ° C). Aqueous solutions of sodium acetate and acetic acid form a buffer solution, that is, the pH remains virtually constant after the addition of ( small amounts ) of acid or alkali.

Use

Sodium acetate is the food additive E 262. It is used as an acidity regulator and preservative for fruits and vegetables in cans and glass jars, bread, fish in all variations, deli salads, mayonnaise and salad dressings. Furthermore, it is used in combination with various fruit acids ( malic acid, citric acid, tartaric acid, etc. ) are present in potato chips the flavor " Salt & Vinegar " as an ingredient.

From supersaturated sodium acetate solution can be simply for demonstration experiments crystals that resemble icebergs produce. For this, seed crystals are placed on the bottom of a beaker and slowly basted with a supersaturated solution of sodium acetate. Immediately form crystals and pile up on a iceberg -like tower.

The so-called " Instant Ice " is based on the same principle. It fills a ( transparent ) vessel on with the solution and touched with the finger tip, the surface of the solution. This crystallized immediately and is solid as ice ( The fingertip replaced here the seed crystal ).

The crystallization of the sodium acetate is highly exothermic, so that this much energy in the form of heat is released. It is used in heat pad, the trihydrate is used as latent heat storage in regenerable hand warmers.

In the waste incineration plant Augsburg a part of the waste heat generated during the incineration is stored in containers with sodium acetate since January 2013 as part of a model project. These are then transported by truck to nearby Friedberg, where the heat is used to heat a school center.

Production

In the laboratory scale, it can be recovered for example by the reaction of sodium carbonate (soda ), and acetic acid:

Likewise, for example, by neutralization of sodium hydroxide with Ethan ( acetic ) acid: