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Systematic name Sodium hydroxymethanesulfinate
Other names Rongalite
Sodium formaldehydesulfoxylate
Molecular formula CH3NaO3S
SMILES C(O)S(=O)[O-].[Na+]
Molar mass 118.10 g/mol
(dihydrate: 154.14 g/mol)
Appearance colorless crystals
CAS number [149-44-0]
(dihydrate: [6035-47-8])
Density and phase dihydrate: 1.75 g/cm3
Solubility in water ca. 600 g/L for dihydrate
Melting point 64.5 °C (dihydrate)
Acidity (pKa) decomp. at low pH
Molecular shape pyramidal at S
MSDS External MSDS
Main hazards non-toxic
NFPA 704
R/S statement R: 36/37/38 S:26-36
RTECS number PB0380000
Supplementary data page
Structure and
n, εr, etc.
Phase behaviour
Spectral data UV, IR, NMR, MS
Related compounds
Related compounds SO32-, CH2O
Except where noted otherwise, data are given for
materials in their standard state (at 25 °C, 100 kPa)
Infobox disclaimer and references

Rongalite, also called Rongalit (registered trademark of BASF) is sodium hydroxymethylsulfinate, or Na+HOCH2SO2-. The salt has many names, including also sodium formaldehyde sulfoxylate. It is water-soluble and generally sold as the dihydrate.



This salt is prepared from sodium dithionite:

Na2S2O4 + 2 CH2O + H2O → NaHOCH2SO3 + NaHOCH2SO2

This reaction proceeds quantitatively, such that dithionite can be determined by its conversion to rongalite, which is far less O2-sensitive and thus easier to handle.

NaHOCH2SO2 can essentially be considered to be a source of SO22-. As such it is used both as a reducing agent and as a reagent to introduce SO2 groups into organic molecules. Treatment of elemental Se and Te with NaHOCH2SO2 gives solutions containing the corresponding Na2Sex and Na2Tex, where x is approximately 2. As a nucleophile, NaHOCH2SO2 reacts with alkylating agents to give sulfones.

NaHOCH2SO2 + 2 C6H5CH2Br → [C6H5CH2]2SO2 + NaBr + CH2O + HBr

Occasionally, alkylation will occur also at oxygen, thus α,α' dibromoxylene gives both the sulfone and the isomeric sulfinate ester.


The compound is used primarily as an industrial bleaching agent.

Zinc formaldehyde sulfoxylate

The zinc complex Zn(HOCH2SO2]2 is marketed under the trademarks Decroline, Decolin, and Safolin. This compound is an additive in polymers and textiles.[1]


  1. ^ Masciocchi, N.; Rigamonti, C. and Maspero, A., "Poly[di-μ3-hydroxymethanesulfinato-zinc(II)]", Acta Crystallographica, Section E: Structure Reports Online, 2005, volume E61, m2683-m2685.
  • Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
  • L. Tschugaeff und W. Chlopin: Beiträge zur Kenntnis des Reduktionsvermögens der schwefligen Säure. I. Einwirkung von Natriumhydrosulfit auf Tellur und Selen" Chemische Berichte 1914, volume 47, pages 1269-1275.
  • R. Steudel, V. Munchow "Determination of dithionite (S2O22- and Hydroxymethanesulphinate (HOCH2SO2-; Rongalite) by Ion-Pair Chromatography" Journal of Chromatography, (1992) volume 623 174-I 77.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Rongalite". A list of authors is available in Wikipedia.
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