Monograph number: 8731
Title: Sodium Bisulfite.
CAS Registry number: [7631-90-5]
Additional name(s): Sodium acid sulfite.
Molecular formula: HNaO3S
Molecular weight: 104.06
Composition: H 0.97%, Na 22.09%, O 46.12%, S 30.81%.
Line formula: NaHSO3.
Literature references: The bisulfite of commerce consists chiefly of sodium metabisulfite, Na2S2O5, and for all practical
purposes possesses the same properties as the true bisulfite. Toxicity: Hoppe, Goble, J. Pharmacol. Exp. Ther. 101, 101
(1951).
Properties: White, crystalline powder; SO2 odor; disagreeable taste; on exposure to air it loses some SO2 and is gradually
oxidized to sulfate. d 1.48. Sol in 3.5 parts cold water, 2 parts boiling water, in about 70 parts alcohol. Its aq soln is
acid. Keep well closed and in a cool place. Incompat: Acids, oxidizers. LD50 i.v. in rats: 115 mg/kg (Hoppe, Goble).
Density: 1.48
Caution: Concd solns are irritating to skin, mucous membranes.
USE: As disinfectant and bleach, particularly for wool; in dyeing for preparing hot and cold indigo vats; in paper-making in place
of sodium hyposulfite to remove Cl from bleached fibers; as stripper (reducer) in laundering; to remove permanganate stains
from skin and clothing; to render certain dyes sol; manuf sodium hydrosulfite; coagulating rubber latex; as preservative for
deteriorative liqs or solns used for technical purposes; as antiseptic in fermentation industries. As preservative and bleach in
food. Pharmaceutic aid (antioxidant).
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Monograph number: 8784
Title: Sodium Metabisulfite.
CAS Registry number: [7681-57-4]
CA name(s): Sodium pyrosulfite.
Molecular formula: Na2O5S2
Molecular weight: 190.11
Composition: Na 24.19%, O 42.08%, S 33.73%.
Line formula: Na2S2O5.
Literature references: Crystallizes from cold water with 7H2O.
Properties: White crystals or powder; odor of SO2. Freely sol in water, glycerol; slightly sol in alcohol. The aq soln is acid.
USE: Pharmaceutic aid (antioxidant).
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Monograph number: 8771
Title: Sodium Hydrosulfite.
CAS Registry number: [7775-14-6]
Additional name(s): Sodium sulfoxylate; sodium dithionite.
Molecular formula: Na2O4S2
Molecular weight: 174.11
Composition: Na 26.41%, O 36.76%, S 36.83%.
Line formula: Na2S2O4.
Literature references: The hydrosulfite of commerce contains 85-90% Na2S2O4.
Properties: White or grayish-white, cryst powder; slight characteristic odor. Oxidizes in air (more readily so in presence of
moisture or when in soln) to bisulfite and bisulfate and acquires an acid reaction. Very sol in water, slightly in alcohol.
Note: The name sodium hydrosulfite is applied also to NaHSO2, mol wt 88.06, sol in water, alcohol. Still more confusion
results when "sodium hyposulfite" is applied to this compd (Na2S2O4) see 1957 Subject Index to Chem. Abstracts, p
2218s under sodium dithionite.
USE: As reducing agent, particularly in dyeing with indigo and vat dyes; bleaching soaps, straw; removing dyes from dyed
fabrics.
Don't cry for me I'm the cleaner