Nomenclature
CAS number: 7757-83-7
Sulfurous acid sodium salt (1:2).
Na
2O
3S; mol wt 126.04.
Na 36.48%, O 38.08%, S 25.44%.
Na
2SO
3.
Properties
Small crystals or powder. It is fairly stable
and does not oxidize as readily as the hydrated sulfite. Sol in 3.2
parts water; sol in glycerol; almost insol in alcohol. pH about 9.
Keep well closed. LD50 i.v. in mice: 175 mg/kg, Hoppe, Goble, J. Pharmacol. Exp. Ther. 101, 101
(1951).Derivative
Heptahydrate.
Nomenclature
CAS number: 10102-15-5
Na
2O
3S.7H
2O; mol wt 252.15.
Na 18.23%, O 63.45%, S 12.72%, H 5.60%.
Properties
Efflorescent crystals. Unstable, oxidizing in
the air to sulfate. Sol in 1.6 parts water, about 30 parts glycerol;
sparingly sol in alc. The aq soln is alkaline and dissolves sulfur.
pH ≈9. Keep well closed in a cool place. Note: The commercial heptahydrate (about 90% pure,
the remainder consisting chiefly of the sulfate) has been largely
replaced by the commercial anhydr salt (about 96-99% pure) which is
more stable.Use
Chiefly in photographic developers and instead of “hypo”
for fixing prints; bleaching wool, straw, silk; generating SO
2; as reducer in manuf dyes; silvering glass; removing traces
of Cl in bleached textiles and paper; preserving meat, egg yolks,
etc. Reducing agent.