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7681-57-4 Usage

Chemical Description

Sodium metabisulfite is an inorganic compound used as a disinfectant, antioxidant, and preservative.


Sodium metabisulfite (chemical formula: Na2S2O5) is a white crystalline or powder solid with a slight sulfur odor. It is toxic upon inhalation and can strongly irritate skin and tissue. It can be decomposed to release toxic oxide fumes of sulfur and sodium upon high temperature. It can be mixed with water to form a corrosive acid. It is generally used as a disinfectant, antioxidant, and preservative agent, as well as a laboratory reagent.
Used in Pulp and Paper Industry:
Sodium metabisulfite is used as a bleach or dechlorinator for improving the quality of paper products.
Used in Photographic Industry:
Sodium metabisulfite is used as a preservative in photo developer solutions, enhancing the stability and performance of photographic materials.
Used in Food Industry:
Sodium metabisulfite is used as a food preservative to maintain the freshness, flavor, and color of various food products and wines.
Used in Chemical Production:
Sodium metabisulfite is used in the manufacture of other chemicals, cleaning agents, detergents, and soaps, contributing to their effectiveness and quality.
Used in Oil and Gas Industry:
Sodium metabisulfite acts as a corrosion inhibitor, protecting equipment and infrastructure from corrosion and extending their lifespan.
Used in Gold Mining Industry:
Sodium metabisulfite is utilized in the precipitation of gold from auric acid and in wastewater treatment to remove hexavalent chromium as trivalent chromium by precipitation after reduction.
Used in Wastewater Treatment:
Sodium metabisulfite plays as an oxygen scavenger to eliminate dissolved oxygen in wastewater and pipes, improving water quality and preventing corrosion.
Used in Polymerization Process:
Sodium metabisulfite may be used as an initiator during the cross-linking polymerization of polybutadiene in the cores of vesicle membranes, enhancing the properties of the final product.
Used in Pharmaceutical Studies:
Sodium metabisulfite may be added as an antioxidant during the preparation of stock solutions of 6-hydroxydopamine in various studies, ensuring the stability and effectiveness of the solutions.
Used in Dechlorination:
Sodium metabisulfite is used for dechlorination in municipal wastewater, pulp & paper, power, and textile water treatment plants, improving water quality and safety.
Used in Dried Fruits:
Sodium metabisulfite is used to preserve flavor, color, and inhibit undesirable microorganism growth in dried fruits.
Used in Shrimp Processing:
Sodium metabisulfite prevents "black spots" due to oxidative deterioration in shrimp, maintaining their quality and appearance.
Used in Maraschino Cherries:
Sodium metabisulfite is used in maraschino cherries to preserve their color and freshness.
Used in Lemon Drinks:
Sodium metabisulfite is found in lemon drinks as a preservative, maintaining their quality and safety.
Used as a Pharmaceutic Aid:
Sodium metabisulfite is used as an antioxidant in the pharmaceutical industry, improving the stability and effectiveness of various medications.


manufactures sodium metabisulfite by reacting sulfur dioxide with sodium carbonate (soda ash), purifying and drying to form crystals or powder. Na2CO3 + 2SO2→Na2S2O5 + CO2

Product Specification

▼▲ Sodium Metabisulfite, wt% 98.7% min. Assay as SO2 66.5 min. Insolubles, wt% ≤ 0.005 Chloride, wt% ≤ 0.05 Thiosulfate, wt% ≤ 0.05 Arsenic, ppm ≤ 1.0 Heavy metals, ppm ≤ 10.0 Iron as (Fe), ppm ≤ 2.0 Selenium, ppm ≤ 5.0 Lead as (Pb), ppm ≤ 2.0

Health Hazard

Sodium metabisulphite is currently listed in Annex III Part B of Directive 95/2/EC as an authorised food additive. As such food labelling is required where sulphite residues exceed 10 mg/kg (ppm). This is labelled E223 with maximum permitted residues in crustacean products set at 150 mg/kg. However it is now accepted that sulphites, when present in foodstuffs, can cause allergic reactions in vulnerable persons and can constitute a danger to health (Collins-Williams, 1983). Metabisulphite is regarded as one causative agent of asthma attacks (Gunnison & Jacobsen, 1987). In accordance with this, EU Directive 2003/89/EC will make allergen labelling a requirement for all food stuffs produced in the European Community, which have been treated with sodium metabisulphite. Sodium metabisulfite typically found in consumer products should pose little a risk of symptoms due to skin or inhalation exposure since sodium metabisulfite is used in very low concentrations. Sodium metabisulfite can produce the following adverse health affects: Contact - Skin exposures can cause symptoms ranging from minor skin irritation or itching to redness and swelling. Eye exposure to sodium metabisulfite may result in redness, tearing or moderate eye irritation. Inhalation - The inhalation of sodium metabisulfite dusts can cause nose and throat irritation or coughing. Repeated or prolonged exposures may cause sore throat or nosebleeds. Inhalation may also cause severe respiratory reactions and aggravate asthma or other breathing diseases. Ingestion - The ingestion of sodium metabisulfite may cause irritation of the mouth and throat, nausea, vomiting and diarrhea. Other Effects - The International Agency for Research on Cancer (IARC) has not classified sodium metabisulfite as a carcinogen (cancer causing).

Health Hazard

Sodium metabisulfite may cause bronchospasm, oculonasal symptoms, and urticaria in sulfite-sensitive individuals; irritation of mucous membranes may occur from inhalation of the dust.


http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_004f/0901b8038004f697.pdf https://en.wikipedia.org/wiki/Sodium_metabisulfite https://pubchem.ncbi.nlm.nih.gov/compound/Sodium_metabisulfite#section=Metabolism-Metabolites

Production Methods

Sodium metabisulfite is prepared by saturating a solution of sodium hydroxide with sulfur dioxide and allowing crystallization to occur; hydrogen is passed through the solution to exclude air. Sodium metabisulfite may also be prepared by saturating a solution of sodium carbonate with sulfur dioxide and allowing crystallization to occur, or by thermally dehydrating sodium bisulfite.


Toxic by inhalation. Upper respiratory tract irritant. Questionable carcinogen.

Flammability and Explosibility


Pharmaceutical Applications

Sodium metabisulfite is used as an antioxidant in oral, parenteral, and topical pharmaceutical formulations, at concentrations of 0.01–1.0% w/v, and at a concentration of approximately 27% w/v in intramuscular injection preparations. Primarily, sodium metabisulfite is used in acidic preparations; for alkaline preparations, sodium sulfite is usually preferred. Sodium metabisulfite also has some antimicrobial activity, which is greatest at acid pH, and may be used as a preservative in oral preparations such as syrups. In the food industry and in wine production, sodium metabisulfite is similarly used as an antioxidant, antimicrobial preservative, and antibrowning agent. However, at concentrations above about 550 ppm it imparts a noticeable flavor to preparations. Sodium metabisulfite usually contains small amounts of sodium sulfite and sodium sulfate.

Contact allergens

This agent is frequently used as a preservative in pharmaceutical products, in the bread-making industry as an antioxidant, and it can induce contact dermatitis. It can be used as a reducing agent in photography and caused dermatitis in a photographic technician, probably acting as an aggravating irritative factor. Sodium metabisulfite contains a certain amount of sodium sulfite and sodium sulfate.

Safety Profile

An inhalation hazard. Poison by intravenous route. Moderately toxic by parenteral route. Experimental reproductive effects. Mutation data reported. When heated to decomposition it emits toxic fumes of SOx and Na2O.


Sodium metabisulfite is widely used as an antioxidant in oral, topical, and parenteral pharmaceutical formulations; it is also widely used in food products. Although it is extensively used in a variety of preparations, sodium metabisulfite and other sulfites have been associated with a number of severe to fatal adverse reactions. These are usually hypersensitivity-type reactions and include bronchospasm and anaphylaxis. Allergy to sulfite antioxidants is estimated to occur in 5–10% of asthmatics, although adverse reactions may also occur in nonasthmatics with no history of allergy. Following oral ingestion, sodium metabisulfite is oxidized to sulfate and is excreted in urine. Ingestion may result in gastric irritation, owing to the liberation of sulfurous acid, while ingestion of large amounts of sodium metabisulfite can cause colic, diarrhea, circulatory disturbances, CNS depression, and death. In Europe, the acceptable daily intake of sodium metabisulfite and other sulfites used in foodstuffs has been set at up to 3.5 mg/kg body-weight, calculated as sulfur dioxide (SO2). The WHO has similarly also set an acceptable daily intake of sodium metabisulfite, and other sulfites, at up to 7.0 mg/kg body-weight, calculated as sulfur dioxide (SO2). LD50 (rat, IV): 0.12 g/kg

Potential Exposure

Sodium metabisulfite is used as an antioxidant in pharmaceutical preparations and as a preservative in foods. People with asthma have a greater chance of having an allergic reaction with this chemical. Individuals allergic to sodium bisulfite (a food preservative found in some wine, fresh shrimp; packaged foods; and restaurant salads and potatoes) may have a severe reaction when exposed to sodium metabisulfite.


Sodium metabisulfite was genotoxic in mice in vivo as determined by chromosomal aberration, micronucleus, and sperm shape assays. It was not mutagenic in bacterial assays.


On exposure to air and moisture, sodium metabisulfite is slowly oxidized to sodium sulfate with disintegration of the crystals. Addition of strong acids to the solid liberates sulfur dioxide. In water, sodium metabisulfite is immediately converted to sodium (Na+) and bisulfite (HSO3-) ions. Aqueous sodium metabisulfite solutions also decompose in air, especially on heating. Solutions that are to be sterilized by autoclaving should be filled into containers in which the air has been replaced with an inert gas, such as nitrogen. The addition of dextrose to aqueous sodium metabisulfite solutions results in a decrease in the stability of the metabisulfite. The bulk material should be stored in a well-closed container, protected from light, in a cool, dry place.


UN1759 Corrosive solids, n.o.s., Hazard class: 8; Labels: 8-Corrosive material, Technical Name required. UN2693 Bisulfites, inorganic, aqueous solutions, n.o.s., Hazard class: 8; Labels: 8-Corrosive material.


Sodium metabisulfite reacts with sympathomimetics and other drugs that are ortho- or para-hydroxybenzyl alcohol derivatives to form sulfonic acid derivatives possessing little or no pharmacological activity. The most important drugs subject to this inactivation are epinephrine (adrenaline) and its derivatives. In addition, sodium metabisulfite is incompatible with chloramphenicol owing to a more complex reaction; it also inactivates cisplatin in solution. It is incompatible with phenylmercuric acetate when autoclaved in eye drop preparations. Sodium metabisulfite may react with the rubber caps of multidose vials, which should therefore be pretreated with sodium metabisulfite solution.


A strong reducing agent. Keep away from oxidizers. Mixtures with water forms a strong corrosive. Contact with acids releases toxic fumes. Heat causes decomposition. Slowly oxidized to the sulfate on exposure to air and moisture. Attacks metals

Regulatory Status

GRAS listed. Accepted for use as a food additive in Europe. Included in the FDA Inactive Ingredients Database (epidural;inhalation; IM and IV injections; ophthalmic solutions; oral preparations; rectal, topical, and vaginal preparations). Included in nonparenteral and parenteral medicines licensed in the UK. Included in the Canadian List of Acceptable Non-medicinal Ingredients.

Check Digit Verification of cas no

The CAS Registry Mumber 7681-57-4 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 7,6,8 and 1 respectively; the second part has 2 digits, 5 and 7 respectively.
Calculate Digit Verification of CAS Registry Number 7681-57:
124 % 10 = 4
So 7681-57-4 is a valid CAS Registry Number.

7681-57-4 Well-known Company Product Price

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  • Alfa Aesar

  • (A17351)  Sodium metabisulfite, 97%   

  • 7681-57-4

  • 500g

  • 206.0CNY

  • Detail
  • Alfa Aesar

  • (A17351)  Sodium metabisulfite, 97%   

  • 7681-57-4

  • 2500g

  • 279.0CNY

  • Detail
  • Alfa Aesar

  • (A17351)  Sodium metabisulfite, 97%   

  • 7681-57-4

  • 10000g

  • 953.0CNY

  • Detail
  • Alfa Aesar

  • (40115)  Sodium metabisulfite, ACS, 97% min   

  • 7681-57-4

  • 500g

  • 261.0CNY

  • Detail
  • Alfa Aesar

  • (40115)  Sodium metabisulfite, ACS, 97% min   

  • 7681-57-4

  • 2.5kg

  • 1076.0CNY

  • Detail
  • Alfa Aesar

  • (33375)  Sodium metabisulfite, SO2 58.5% min   

  • 7681-57-4

  • 500g

  • 123.0CNY

  • Detail
  • Alfa Aesar

  • (33375)  Sodium metabisulfite, SO2 58.5% min   

  • 7681-57-4

  • 2kg

  • 389.0CNY

  • Detail
  • Sigma-Aldrich

  • (PHR1434)  Sodium Metabisulfite  pharmaceutical secondary standard; traceable to USP

  • 7681-57-4

  • PHR1434-1G

  • 791.15CNY

  • Detail
  • Sigma-Aldrich

  • (31448)  Sodiummetabisulfite  puriss. p.a., ACS reagent, reag. Ph. Eur., dry, 98-100.5%

  • 7681-57-4

  • 31448-140G-KC

  • 0.00CNY

  • Detail
  • Sigma-Aldrich

  • (31448)  Sodiummetabisulfite  puriss. p.a., ACS reagent, reag. Ph. Eur., dry, 98-100.5%

  • 7681-57-4

  • 31448-500G

  • 682.11CNY

  • Detail
  • Sigma-Aldrich

  • (31448)  Sodiummetabisulfite  puriss. p.a., ACS reagent, reag. Ph. Eur., dry, 98-100.5%

  • 7681-57-4

  • 31448-1KG

  • 1,041.30CNY

  • Detail
  • Sigma-Aldrich

  • (31448)  Sodiummetabisulfite  puriss. p.a., ACS reagent, reag. Ph. Eur., dry, 98-100.5%

  • 7681-57-4

  • 31448-2.5KG

  • 2,307.24CNY

  • Detail



According to Globally Harmonized System of Classification and Labelling of Chemicals (GHS) - Sixth revised edition

Version: 1.0

Creation Date: Aug 16, 2017

Revision Date: Aug 16, 2017


1.1 GHS Product identifier

Product name Sodium metabisulfite

1.2 Other means of identification

Product number -
Other names Sodium pyrosulfite

1.3 Recommended use of the chemical and restrictions on use

Identified uses For industry use only. Preservatives and Antioxidants
Uses advised against no data available

1.4 Supplier's details

1.5 Emergency phone number

Emergency phone number -
Service hours Monday to Friday, 9am-5pm (Standard time zone: UTC/GMT +8 hours).

More Details:7681-57-4 SDS

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