Substance profile
Sodium Dithionite
Sodium Dithionite is a white or grayish-white crystalline powder with a faint sulfurous odor.
01 · Identification
What Sodium Dithionite is
Sodium Dithionite is a white or grayish-white crystalline powder with a faint sulfurous odor. It melts at 52 °C.
Under the GHS it carries the signal word Danger. It is classed as reactive agents - 2nd degree.
02 · Identifiers
Sodium Dithionite identifiers and molecular data
Sodium Dithionite CAS number and EC number
Sodium Dithionite molecular formula and molecular weight
Other names for Sodium Dithionite
- sodium hydrosulphite
03 · GHS classification
Sodium Dithionite hazard classification
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
Sodium Dithionite pictograms and signal word
Sodium Dithionite hazard class and category
| Hazard class | Category | From code | Pictogram |
|---|---|---|---|
| Self-heating substances and mixtures GHS chapter 2.11 | Category 1 | H251 | GHS02 |
| Acute toxicity - oral GHS chapter 3.1 | Category 4 | H302 | GHS07 |
Sodium Dithionite hazard statements (H-codes)
| Code | Hazard statement |
|---|---|
| H251 | Self-heating: may catch fire. |
| H302 | Harmful if swallowed. |
Sodium Dithionite supplemental EU statements (EUH)
| Code | Statement |
|---|---|
| EUH031 | Contact with acids liberates toxic gas. |
This page lists only the codes assigned to Sodium Dithionite. The full reference lives on the hazard statements hub, the precautionary statements hub and the GHS pictograms hub.
Safety Data Sheet
Getting an SDS for Sodium Dithionite
A Safety Data Sheet is written for a product, not for a substance: the supplier of the grade you actually buy issues it, so two suppliers of Sodium Dithionite issue two different sheets. That is why there is no single authoritative SDS for a substance to download — what there is, is the job of collecting the sheets for the products you hold and keeping them current as suppliers revise them.
04 · Precautionary statements
Sodium Dithionite precautionary statements
CLP Annex VI assigns 4 precautionary statements to Sodium Dithionite. They are grouped the way a label groups them: what to do before handling, what to do when something has already happened, how to store it and how to dispose of it.
Prevention
What to do before and during handling so the hazard never happens.
Response
What to do once exposure, spillage or fire has already happened.
Reading the notation. … is a blank the supplier fills in — not a truncated sentence.· [square brackets] mark a part printed only when it applies.
05 · Names in the regulation
Sodium Dithionite name in 23 EU languages
CLP Annex VI Part 3 is published in every language edition of the regulation, and the identification column is written out in each of them. Nothing below is translated by us: each line is the name as that edition prints it. Under Art. 18(2) the substance name from Annex VI is a lawful product identifier, so this is the wording to put on a label going to that market — and where the cell lists several designations, any one of them qualifies.
| Language | Name in CLP Annex VI Part 3 |
|---|---|
| Bulgarian български | натриев дитионит натриев хидросулфит |
| Spanish español | Ditionito de sodio hidrosulfito de sodio |
| Czech čeština | dithioničitan sodný |
| Danish dansk | natriumdithionit natriumhydrosulfit |
| German Deutsch | Natriumdithionit Natriumhydrosulfit |
| Estonian eesti | naatriumditionit naatriumhüdrosulfit |
| Greek ελληνικά | διθειονώδες νάτριο υδροθειώδες νάτριο |
| English English | sodium dithionite sodium hydrosulphite |
| French français | dithionite de sodium hydrosulfite de sodium |
| Croatian hrvatski | natrijev ditionit natrijev hidrosulfit |
| Italian italiano | sodium dithionite sodio idrosolfito |
| Latvian latviešu | nātrija ditionīts nātrija hidrosulfīts |
| Lithuanian lietuvių | natrio ditionitas natrio hidrosulfitas |
| Hungarian magyar | nátrium-ditionit nátrium-hidroszulfit |
| Maltese Malti | ditijonit tas-sodju idrosulfit tas-sodju |
| Dutch Nederlands | natriumdithioniet natriumhydrosulfiet |
| Polish polski | ditionian(III) sodu podsiarczyn sodu |
| Portuguese português | ditionito de sódio hidrossulfito de sódio |
| Romanian română | ditionit de sodiu hidrosulfit de sodiu |
| Slovak slovenčina | ditioničitan sodný |
| Slovenian slovenščina | natrijev ditionit natrijev hidrosulfit |
| Finnish suomi | natriumditioniitti natriumhydrosulfiitti |
| Swedish svenska | natriumditionit natriumhydrosulfit |
All 23 language editions of Annex VI carry this entry. Irish is the twenty-fourth official EU language and has no line here for a different reason: no consolidated CLP text has ever been published in Irish, so there is no Irish edition of Annex VI to quote a name from. Source: consolidated CLP, CELEX 02008R1272, language editions. © European Union, https://eur-lex.europa.eu — only the electronic Official Journal of the European Union is authentic.
06 · Label elements
Sodium Dithionite GHS label elements
Everything CLP Annex VI fixes for Sodium Dithionite, laid out the way it appears on a label. The greyed lines are the parts only the supplier can fill in.
Danger
Sodium Dithionite
- Self-heating: may catch fire.
- Harmful if swallowed.
- Contact with acids liberates toxic gas.
- Do not eat, drink or smoke when using this product.
- IF SWALLOWED:
- Call a POISON CENTER/doctor/… if you feel unwell.
- Rinse mouth.
Supplier name, address and telephone number· Product identifier·Nominal quantity
Need this as an actual label? Open Sodium Dithionite in the GHS label constructor →
07 · Health hazards
Sodium Dithionite health hazards and exposure limits
Sodium Dithionite hazard summary
A skin and eye irritant; Reacts with acids and hot water to form oxides of sulfur; Inhalation of high concentrations may cause acute pneumonitis; [CHEMINFO MSDS] Reacts with water to form hydrogen sulfide and sulfur dioxide; [ERG 2016]
Source: Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
08 · Physical and chemical properties
Sodium Dithionite properties
Every value is shown with the conditions it was measured under and the source it came from. Where sources disagree, all values are listed rather than one being picked — the difference is usually a different form of the substance, not an error.
Sodium Dithionite melting point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Melting point | 52 °C (125.6 °F) | decomposes, decomposes | HSDB |
Sodium Dithionite density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Density | 2.38 g/cm³ | HSDB | |
| 1.58 g/cm³ | Dihydrate | HSDB | |
| 2.4 g/cm³ | ICSC |
Sodium Dithionite solubility
| Property | Value | Conditions | Source |
|---|---|---|---|
| Solubility | Slightly sol in alcohol; very soluble in water | HSDB | |
| Slightly sol in cold water; insoluble in acids | HSDB | ||
| At 20 °C, 24.1 g/100 g water | at 20 °C | HSDB |
Sodium Dithionite flash point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Flash point | 100 °C (212 °F) | approximate, open cup | HSDB |
| 100 °C (212 °F) | above this value | ICSC |
Sodium Dithionite autoignition temperature
| Property | Value | Conditions | Source |
|---|---|---|---|
| Autoignition temperature | 190 °C (374 °F) | approximate | HSDB |
Sodium Dithionite lower explosive limit (LEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Lower explosive limit (LEL) | Combustible solid but not explosive. | HSDB | |
| Closed containers may rupture violently when heated. | HSDB |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
09 · Fire and explosion
Sodium Dithionite fire and explosion behaviour
These are descriptions rather than measured values, so they are kept out of the table above and quoted here with the source that reported them.
Sodium Dithionite fire potential
Combustible solid. Easily oxidized. Heats spontaneously in contact with moisture and air, and may ignite surrounding combustible materials. Closed containers may rupture violently when heated.
Source: Hazardous Substances Data Bank (HSDB)
10 · Handling and storage
Sodium Dithionite storage and handling
Sodium Dithionite safe storage
Dry. Well closed. Separated from strong oxidants and acids. Store in an area without drain or sewer access.
Source: ILO-WHO International Chemical Safety Cards (ICSCs)
Sodium Dithionite storage conditions
Store in cool place. Keep container tightly closed in a dry and well-ventilated place. Do not store near acids. Air sensitive. Heat sensitive. Moisture sensitive. Handle under inert gas. Protect from moisture.
Source: Hazardous Substances Data Bank (HSDB)
Sodium Dithionite incompatible materials
Use of scoop contaminated with sodium dithionite for sodium chlorite caused ignition of latter. Material containing sulfur (dithionite, natural rubber gloves) cause decomp of sodium chlorite and contact should be avoided.
Source: Hazardous Substances Data Bank (HSDB)
Sodium Dithionite reactivity
Sodium dithionite is a combustible solid which slowly decomposes when in contact with water or water vapor, forming thiosulfates and bisulfites. This reaction evolves heat, which can further accelerate the reaction or cause surrounding materials to burn. If the mixture is confined, the decomposition reaction can result in pressurization of the container which may then rupture forcefully. Upon standing in air it slowly oxidizes, generating toxic sulfur dioxide gas. (NFPA, 2010)
Source: CAMEO Chemicals
Planning storage for a mix of chemicals? Check Sodium Dithionite in the storage compatibility matrix →
11 · Transport
Sodium Dithionite UN number and transport classification
Transport classification is a separate system from the GHS classification above. It decides how a package is marked and how a load may be carried; it does not follow from the workplace label, and the workplace label does not follow from it. The entries below are linked by CAS number, never by name.
Sodium Dithionite under UN 1384 — shipping name, class and packing group
Europe · ADR 2025, Table A
| Proper shipping name (3.1.2) | Class | Classification code | PG | Labels (column 5) |
|---|---|---|---|---|
| SODIUM DITHIONITE (SODIUM HYDROSULPHITE) | 4.2 | S4 | II | |
Source: ADR 2025, Table A of Chapter 3.2 · ECE/TRANS/352 Vol. I (UNECE). Class 4.2 is “Substances liable to spontaneous combustion” (ADR 2.1.1.1).
United States · 49 CFR 172.101 Hazardous Materials Table
| Proper shipping name (column 2) | Class or division | PG | Labels (column 6) |
|---|---|---|---|
| Sodium dithionite or Sodium hydrosulfite | 4.2 | II | |
Source: 49 CFR 172.101 Hazardous Materials Table · eCFR, revision 2026-08-03. Class 4.2 is “Spontaneously combustible material” (49 CFR 173.2).
12 · Questions
Sodium Dithionite — frequently asked questions
What is the CAS number of Sodium Dithionite?
The CAS number of Sodium Dithionite is 7775-14-6. Its EC number is 231-890-0.
What does a Sodium Dithionite label have to show?
Under CLP Annex VI the label for Sodium Dithionite carries the pictograms Flame and Exclamation mark and the signal word is Danger.
Is Sodium Dithionite flammable?
Yes. CLP Annex VI assigns Sodium Dithionite H251 — self-heating: may catch fire. The flash point reported for it is 100 °C (212 °F), approximate, open cup (HSDB).
Is Sodium Dithionite a carcinogen?
CLP Annex VI records no harmonised carcinogenicity classification for Sodium Dithionite. Annex VI is a list of agreed classifications, not a list of substances found safe, so this is an absence of a classification rather than a clean bill of health.
What is the melting point of Sodium Dithionite?
The melting point reported for Sodium Dithionite is 52 °C (125.6 °F), decomposes, decomposes (HSDB).
How should Sodium Dithionite be stored?
Store in cool place. Keep container tightly closed in a dry and well-ventilated place. Do not store near acids. Air sensitive. Heat sensitive. Moisture sensitive. Handle under inert gas. Protect from moisture. (Hazardous Substances Data Bank (HSDB))
Nearby
Substances next to Sodium Dithionite
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