8430. Selenious Acid

Nomenclature

CAS number: 7783-00-8
Monohydrated selenium dioxide; selenous acid.
H2O3Se; mol wt 128.97.
H 1.56%, O 37.22%, Se 61.22%.
H2SeO3.

Description and references

Prepd by dissolving selenium dioxide in hot water and cooling: Berzelius, Acad. Handl. Stockholm 39, 13 (1818).

Properties

Deliquescent hexagonal prisms; d415 3.004. Vapor press. (mm Hg): 2 at 15°; 4.5 at 35°; 7 at 40.3°. K1 = 0.0024; K2 = 4.8 × 10-9. Gives off water upon heating and selenium oxide sublimes. Oxidized to selenic acid by strong oxidizing agents such as ozone, hydrogen dioxide, chlorine. Reduced to selenium by most reducing agents including hydriodic acid, sulfurous acid, sodium hyposulfite, hydroxylamine salts, hydrazine salts, hypophosphorous acid, phosphorous acid. 90 parts dissolve in 100 parts water at 0°, 400 parts at 90°; very sol in alcohol; insol in ammonia.

Use

As a reagent for alkaloids; as oxidizing agent.