Sodium Pyrosulfite

1Identification

Name

Sodium Pyrosulfite

CAS number

7681-57-4

EC number

231-673-0

Molecular formula

Na2O5S2

Molecular weight

190.11 g/mol

InChIKey

HRZFUMHJMZEROT-UHFFFAOYSA-L

SMILES

[O-]S(=O)S(=O)(=O)[O-].[Na+].[Na+]

PubChem CID

656671

Synonyms

Sodium metabisulfite, Sodium pyrosulfite, Sodium disulfite, Disodium pyrosulfite, Natrii disulfis, Campden Tablets, Disodium metabisulfite, Natrium pyrosulfit, Natriummetabisulfit, sodium pyrosulphite, Sodium bisulfite anhydrous, Natrium metabisulfurosum, Sodium pyrosulfite (Na2S2O5), Disodium pentaoxodisulfate

Recommended uses

• CIR ingredient: Sodium Metabisulfite
  Cosmetic Ingredient Review (CIR)
• Sodium and potassium metabisulfite are used as antioxidants in photographic film development. [Kanerva, p. 1637] Used as an antioxidant (food preservative, pharmaceutical aid, silage preservative; [HSDB] Used in the pickling stage of leather production; [PMID 21938525]
  Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
• Leather Tanning and Processing [Category: Industry] Photographic Processing [Category: Other]
  Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
• Reducing agent Preservative Not Known or Reasonably Ascertainable Etching agent Flotation agent Anti-scaling agent Intermediate Oxidizing agent Dye Leaching agent Processing aids not otherwise specified Surfactant (surface active agent) Chemical reaction regulator Antioxidant
  EPA Chemical Data Reporting (CDR)
• Solvent Processing aids not otherwise specified Not Known or Reasonably Ascertainable Reducing agent Flotation agent Etching agent
  EPA Chemical Data Reporting (CDR)

Use categories: EPA Safer Chemical Functional Use Classes -> Preservatives and Antioxidants · Safer Chemical Classes -> Yellow triangle - The chemical has met Safer Choice Criteria for its functional ingredient-class, but has some hazard profile issues · Food additives · Food Additives -> ANTIOXIDANT; FLOUR_TREATMENT_AGENT; PRESERVATIVE -> JECFA Functional Classes

Description

• Sodium metabisulfite appears as a white crystalline or powder solid with a slight sulfur odor. Toxic by inhalation. Strongly irritates skin and tissue. Noncombustible, but may decompose to emit toxic oxide fumes of sulfur and sodium when heated to high temperature. A corrosive acid when mixed with water. Used as a food preservative and as a laboratory reagent.
  CAMEO Chemicals
• Sodium disulfite is an inorganic sodium salt composed of sodium and disulfite ions in a 2:1 ratio. It has a role as a food antioxidant. It contains a disulfite.
  ChEBI
• request from searcher; RN given refers to disulfurous acid, di-Na salt
  Medical Subject Headings (MeSH)

2Hazard identification

Signal word

Danger

Pictograms

GHS05, GHS07

Classification source

Regulation (EC) No 1272/2008 of the European Parliament and of the Council

Precautionary statements

Other reported classifications

6 classification records exist across sources. Differences usually reflect purity, physical form or impurities.

Health hazards

• Excerpt from NIOSH Pocket Guide for Sodium metabisulfite: Exposure Routes: Inhalation, ingestion, skin and/or eye contact Symptoms: Irritation eyes, skin, mucous membrane Target Organs: Eyes, skin, respiratory system (NIOSH, 2024)
  CAMEO Chemicals

Fire hazards

• Excerpt from ERG Guide 154 [Substances - Toxic and/or Corrosive (Non-Combustible)]: Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive and/or toxic fumes. Some are oxidizers and may ignite combustibles (wood, paper, oil, clothing, etc.). Corrosives in contact with metals may evolve flammable hydrogen gas. Containers may explode when heated. For electric vehicles or equipment, ERG Guide 147 (lithium ion or sodium ion batteries) or ERG Guide 138 (sodium batteries) should also be consulted. (ERG, 2024)
  CAMEO Chemicals
• Not combustible. Gives off irritating or toxic fumes (or gases) in a fire. Risk of fire and explosion on contact with acids or oxidants.
  ILO-WHO International Chemical Safety Cards (ICSCs)

Hazards summary

• A case of occupational asthma, confirmed by specific inhalation challenge, was reported in which a worker sprinkled dry metabisulfite on potatoes. [Malo JL, Cartier A, Desjardins A. Occupational asthma caused by dry metabisulphite. Thorax 1995 May;50(5); 585-6.] Similar cases have been reported in the wine, laundry, and lobster fishing industries. [Madsen J, Sherson D, Kjoller H, Hansen I, Rasmussen K. Occupational asthma caused by sodium disulphite in Norwegian lobster fishing. Occup Environ Med 2004;61:873-874] Occupational skin sensitization has also been reported; [Sulfite contact allergy. Vena GA, Foti C, Angelini G.
  Haz-Map, Information on Hazardous Chemicals and Occupational Diseases

3Composition / information on ingredients

This page describes the pure substance. Commercial products may be solutions or mixtures. Check Section 3 of your supplier's SDS for concentrations and other ingredients.

4First-aid measures

• Excerpt from NIOSH Pocket Guide for Sodium metabisulfite: Eye: IRRIGATE IMMEDIATELY - If this chemical contacts the eyes, immediately wash (irrigate) the eyes with large amounts of water, occasionally lifting the lower and upper lids. Get medical attention immediately. Breathing: FRESH AIR - If a person breathes large amounts of this chemical, move the exposed person to fresh air at once. Other measures are usually unnecessary. Swallow: MEDICAL ATTENTION IMMEDIATELY - If this chemical has been swallowed, get medical attention immediately. (NIOSH, 2024)
  CAMEO Chemicals
• (General first aid procedures) Eye: Irrigate immediately - If this chemical contacts the eyes, immediately wash (irrigate) the eyes with large amounts of water, occasionally lifting the lower and upper lids. Get medical attention immediately. Breathing: Fresh air Swallow: Medical attention immediately - If this chemical has been swallowed, get medical attention immediately.
  The National Institute for Occupational Safety and Health (NIOSH)

Symptoms of exposure

• Cough. Shortness of breath. Wheezing.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• Redness.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• Redness. Burning sensation. Pain.
  ILO-WHO International Chemical Safety Cards (ICSCs)

5Fire-fighting measures

• If material /is/ involved in /a/ fire: Use dry chemical, dry sand, or carbon dioxide. Do not use water on material itself. If large quantities of combustibles are involved, use water in flooding quantities as spray and fog. Cool all affected containers with flooding quantities of water. Apply water from as far a distance as possible.
  Hazardous Substances Data Bank (HSDB)

6Accidental release measures

Isolation and evacuation

• Excerpt from ERG Guide 154 [Substances - Toxic and/or Corrosive (Non-Combustible)]: IMMEDIATE PRECAUTIONARY MEASURE: Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters (75 feet) for solids. SPILL: Increase the immediate precautionary measure distance, in the downwind direction, as necessary. FIRE: If tank, rail tank car or highway tank is involved in a fire, ISOLATE for 800 meters (1/2 mile) in all directions; also, consider initial evacuation for 800 meters (1/2 mile) in all directions. (ERG, 2024)
  CAMEO Chemicals

Spill cleanup

• Personal protection: filter respirator for acid gases and vapours adapted to the airborne concentration of the substance. Collect leaking and spilled liquid in covered non-metallic containers as far as possible. Absorb liquid in sand or inert absorbent. Wash away remainder with plenty of water. Then store and dispose of according to local regulations.
  ILO-WHO International Chemical Safety Cards (ICSCs)

7Handling and storage

• Separated from acids, strong oxidants and food and feedstuffs. Well closed.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• The bulk material should be stored in a well closed container, protected from light, in a cool, dry place.
  Hazardous Substances Data Bank (HSDB)
• ... Storage containers are predominantly made from 1.4571 grade stainless steel. Fiberglass-reinforced plastic containers are also suitable for storage. Paper or plastic sacks, steel barrels, or big bags made of synthetic fibers are used for transportation.
  Hazardous Substances Data Bank (HSDB)

8Exposure controls / personal protection

Personal protective equipment

• Excerpt from NIOSH Pocket Guide for Sodium metabisulfite: Skin: No recommendation is made specifying the need for personal protective equipment for the body. Eyes: No recommendation is made specifying the need for eye protection. Wash skin: No recommendation is made specifying the need for washing the substance from the skin (either immediately or at the end of the work shift). Remove: No recommendation is made specifying the need for removing clothing that becomes wet or contaminated. Change: No recommendation is made specifying the need for the worker to change clothing after the workshift. (NIOSH, 2024)
  CAMEO Chemicals
• /NIOSH certified respirator/; goggles or face shield.
  Hazardous Substances Data Bank (HSDB)

Respirator recommendations

• Important additional information about respirator selection
  The National Institute for Occupational Safety and Health (NIOSH)

9Physical and chemical properties

10Stability and reactivity

Reactivity

• SODIUM METABISULFITE is incompatible with the following: Heat (decomposes) [Note: Slowly oxidized to the sulfate on exposure to air & moisture.] (NIOSH, 2024).
  CAMEO Chemicals
• Acts as a corrosive acid when mixed with water. Reacts slowly with air and water.
  CAMEO Chemicals

Incompatible materials and hazardous reactions

• Large scale addition of solid sodium disulfite to an unstirred and too-concentrated solution of sodium nitrite caused a vigorous exothermic reaction.
  Hazardous Substances Data Bank (HSDB)
• Heat (decomposes) [Note: Slowly oxidized to the sulfate on exposure to air & moisture.]
  The National Institute for Occupational Safety and Health (NIOSH)

Chemical stability

• On exposure to air and moisture is slowly oxidized to sulfate.
  Hazardous Substances Data Bank (HSDB)

11Toxicological information

Target organs

• Eyes, skin, respiratory system
  The National Institute for Occupational Safety and Health (NIOSH)

Short-term exposure effects

• The substance is severely irritating to the eyes. The substance is irritating to the skin, respiratory tract and gastrointestinal tract. Exposure could cause asthma-like reactions or urticaria in sensitive persons.
  ILO-WHO International Chemical Safety Cards (ICSCs)

Long-term exposure effects

• Repeated or prolonged inhalation may cause asthma-like symptoms. The substance may have effects on the skin.
  ILO-WHO International Chemical Safety Cards (ICSCs)

12Ecological information

Not available in the public sources we compile. Check Section 12 of the supplier's SDS.

13Disposal considerations

• SRP: The most favorable course of action is to use an alternative chemical product with less inherent propensity for occupational harm/injury/toxicity or environmental contamination. Recycle any unused portion of the material for its approved use or return it to the manufacturer or supplier. Ultimate disposal of the chemical must consider: the material's impact on air quality; potential migration in soil or water; effects on animal and plant life; and conformance with environmental and public health regulations.
  Hazardous Substances Data Bank (HSDB)

14Transport information

DOT label

• Corrosive
  CAMEO Chemicals

UN classification

• UN Hazard Class: 8; UN Pack Group: I, II, III
  ILO-WHO International Chemical Safety Cards (ICSCs)

Not available in the public sources we compile. Check Section 14 of the supplier's SDS.

How DOT hazard classes work →

15Regulatory information

• Section 8(a) of TSCA requires manufacturers of this chemical substance to report preliminary assessment information concerned with production, exposure, and use to EPA as cited in the preamble in 51 FR 41329. Effective date 1/26/94; Reporting date: 3/28/94.
  Hazardous Substances Data Bank (HSDB)
• Sodium metabisulfite used as a chemical preservative in food for human consumption is generally recognized as safe when used in accordance with good manufacturing practice, except that it is not used in meats; in food recognized as a source of vitamin B1; on fruits or vegetables intended to be served raw to consumers or sold raw to consumers, or to be presented to consumers as fresh.
  Hazardous Substances Data Bank (HSDB)

Overview of SDS regulations (OSHA HazCom, WHMIS, REACH/CLP) →

16Other information

Compiled from PubChem CID 656671 and the sources it aggregates (attributed inline). Data retrieved 2026-10-12. This summary describes the pure substance and is not a supplier SDS.