Sodium metabisulfite

• Sodium metabisulfite
• Pyrosulfite
• E 223

White to pale yellow crystalline solid with a pungent odor

Fixed

2.36 g · cm -3 at 20 ° C.

Decomposition above 150 ° C.

Soluble in water ( approximately 650 g · l-1 at 20 ° C)

Risk

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Sodium disulfite ( Na2S2O5 ) also called sodium pyrosulfite or sodium metabisulfite, is a sodium salt is not stable in its free form disulfurous acid. Disulfites have a fairly long time, so little stable sulfur -sulfur bond. In water, therefore, the hydrolysis is easy to sodium bisulfite:

On heating the salt thermal decomposition takes place with elimination of sulfur dioxide ( SO2):

Synthesis

It is produced by thermal dimerization (condensation) of sodium bisulfite with elimination of water (1), or by reaction of sulfur dioxide and sodium in sodium hydroxide solution (2):

Use

In the Federal Republic of Germany is sodium ( E 223 ) used as a food additive, especially as a preservative and antioxidant. It is used in horseradish mixture, fruit and vegetable preparations, potato dishes, ready meals, fruit juices and jams in dried fruit. It is also used in combination with sorbic acid and benzoic acid. It can be used for diagnosis of the sickle cell test in order to escape the hemoglobin in sickle cell anemia and oxygen to accelerate a sickling.

Sodium is used as a reducing agent in the chemical fiber production, for the detoxification of chromium-containing wastewater from the Galvanobetriebe as well as in the photographic industry and building chemistry.

Others

Sodium can be especially easily confused with sodium bisulfite, an older but still common names for sodium bisulfite.

Health

Sodium is rapidly degraded by an endogenous enzyme in most people in the present in food concentrations, but would otherwise lead to nausea, vomiting, diarrhea and headache. In asthmatics, it can trigger Sulfitasthma; also allergic and allergic-like reactions are possible, although rare. In foods, sodium vitamin destroyed B1 ( thiamine).

The effects of sodium on human health and the environment are tested under REACH in 2014 under substance evaluation of Hungary.