Disulfites

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Structure of the disulfide - ion

Disulfites are also called pyrosulfites or disulfates (IV) and are salts of disulfurous acid (H 2 S 2 O 5 ) which does not exist in free form . The disulfites have the general formula M 2 S 2 O 5 (with M = monovalent metal, such as K or Na ). They can be regarded as an addition compound of sulfur dioxide SO 2 and sulphurous acid H 2 SO 3 .

Formally, the disulfites are based on disulfurous acid, which is also called pyrosulfuric acid or disulfuric acid (IV) . Disulfurous acid has not yet been isolated as a substance; it is only stable in the form of its salts.

synthesis

Disulfites are formed when SO 2 is introduced into aqueous solutions of alkali hydrogen sulfites.

Synthesis of disulfites from alkali hydrogen sulfites with sulfur dioxide

When concentrating a solution of hydrogen sulfites form under dehydration Disulfite.

properties

The bisulfite anion has quite a long, little stable sulfur -sulfur Binding: [O 2 S-SO 3 ] 2- (220.5 pm; the length of a typical S-S-C single bond is 208 pm). In aqueous solution, hydrolysis in hydrogen sulfites HSO 3 - is therefore easy .

use

Disulfites have the same practical uses as sulfites and can be used as reducing agents. As a food additive , they are used as preservatives , antioxidants or color stabilizers .

Examples

See also

Individual evidence

  1. ↑ a b Hans P. Latscha, Helmut A. Klein; Inorganic Chemistry: Basic Chemistry I ; ISBN 978-3-540-69863-0 , p. 370.
  2. ↑ Waldemar Ternes; Food lexicon; ISBN 978-3899471656 .
  3. ↑ a b Entry on disulfurous acid. In: Römpp Online . Georg Thieme Verlag, accessed on March 20, 2016.
  4. ^ A b Karl-Heinz Lautenschläger, Werner Schröter; Taschenbuch der Chemie, p. 501; ISBN 978-3817117611 .