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Home> Encyclopedia >Textile Auxiliary Agents>Organic Intermediate>Sulphate
Disodium hydrosulfite structure
Disodium hydrosulfite structure

Disodium hydrosulfite

CAS No.: 7775-14-6
Molecular Weight:174.096
Modify Date.: 2022-11-12 07:19
Introduction: Sodium dithionite is also called sodium hydrosulfite, sodium hydrosulphite, sodium sulfoxylate, and sulfoxylate. Sodium dithionite is not stable under physiological conditions, with the rate of decomposition increasing with increasing acidity. Upon contact with moisture, it is oxidized to hydrogen sulfite (HSO3-), sulfite (SO32-) and hydrogen sulfate (HSO4-). Under strongly acidic conditions it may liberate sulfur dioxide. Under anaerobic conditions (such as in the lower gastrointestinal tract), hydrogen sulfite (HSO3-) and thiosulfate (S2O32-) may be formed. Hydrogen sulfite (HSO3-) can be absorbed after ingestion. It is efficiently metabolized and the major part rapidly is excreted as sulfate into the urine. View more+
1. Names and Identifiers
1.1 Name
Disodium hydrosulfite
1.2 Synonyms

Blankit Burmol Disodium dithionite Dithionous acid, disodium salt Dithionous acid,disodium salt EINECS 231-890-0 MFCD00011640 Sodium dithionite SODIUM HYDROSULFITE Sodium hypodisulfite Sodium sulfoxylate Vatrolite

1.3 CAS No.
1.4 CID
1.6 Molecular Formula
Na2O4S2 (isomer)
1.7 Inchi
1.8 InChkey
1.9 Canonical Smiles
1.10 Isomers Smiles
2. Properties
2.1 Density
2.1 Melting point
300℃ (dec.)
2.1 Boiling point
2.1 Flash Point
>100°C o.c.
2.1 Precise Quality
2.1 PSA
2.1 logP
2.1 Solubility
250 g/L (20 ºC)
2.2 Appearance
White solid
2.3 Storage
Sodium dithionite crystals are available in steel containers (1 or 2 tons) or in steel drums (200 kg). Because of the danger of spontaneous ignition in humid air, sodium dithionite must be stored under dry and cool conditions. The sites for the preparation of dithionite solutions must permit handling without risks, high humidity should be avoided and remote fire control should be available.Commercial dithionite products are classified as self-igniting hazardous goods (Class 4.2, UN 1384). Local rules for transportation and storage must be obeyed. Disodium hydrosulfite Preparation Products And Raw materials Raw materials
2.4 Autoignition Temperature
about 190 deg C
2.5 Chemical Properties
White solid
2.6 Color/Form
White or grayish-white crystalline powder
Light-lemon-colored solid in powder or flake form
White, colorless or yellow-white crystals
2.7 Decomposition
A batch decomposed violently during drying in graining bowl. No explanation was offered but contamination with water; and/or oxidant seems likely. Thermal decomposition occurs violently at 190 deg C.
2.8 Odor
Faint sulfurous
2.9 PH
5.5-8.5 (50g/l, H2O, 20℃)
2.10 Physical
Sodium dithionite; is a whitish to light yellow crystalline solid having a sulfur dioxide;-like odor. It spontaneously heats on contact with air and moisture. This heat may be sufficient to ignite surrounding combustible materials. Under prolonged exposure to fire or intense heat containers of this material may violently rupture. It is used in dyeing and to bleach paper pulp.
2.11 Water Solubility
250 g/L (20 oC)
2.12 Stability
Stable, but air sensitive. Incompatible with strong acids, strong oxidizing agents, water, moisture.
2.13 StorageTemp
Store at RT.
3. Use and Manufacturing
3.1 Definition
ChEBI: An inorganic sodium salt that is the disodium salt of dithionous acid.
3.2 General Description
Sodium dithionite is a whitish to light yellow crystalline solid having a sulfur dioxide-like odor. Sodium dithionite spontaneously heats on contact with air and moisture. This heat may be sufficient to ignite surrounding combustible materials. Sodium dithionite is soluble in water. Under prolonged exposure to fire or intense heat containers of Sodium dithionite may violently rupture. Sodium dithionite is used in dyeing and to bleach paper pulp.
3.3 GHS Classification
Signal: Danger
GHS Hazard Statements
H251: Self-heating; may catch fire [Danger Self-heating substances and mixtures]
H302: Harmful if swallowed [Warning Acute toxicity, oral]

Precautionary Statement Codes
P235+P410, P264, P270, P280, P301+P312, P330, P407, P413, P420, and P501
3.4 Methods of Manufacturing
Zinc; dust process: ... An aqueous slurry of zinc; dust is treated in a stirred reactor with cooling at ca. 40 deg C with liquid or gaseous sulfur dioxide; to give zinc dithionite;. After completion of the reaction the solution is passed through a filter press to remove unreacted zinc; dust and impurities from the zinc;. The zinc; is then precipitated from the zinc dithionite; by adding sodium carbonate; or sodium hydroxide; in stirred vessels. The zinc carbonate; or hydroxide; is removed in filter presses. Anhydrous sodium dithionite; is precipitated from the clarified sodium dithionite; solution by concentration under vacuum and addition of sodium chloride; at > 60 deg C. It is filtered, washed with methanol;, and dried at 90 - 100 deg C. Besides the evaporation process the salting out process, which was more widely used previously, is still known. In this process the dithionite; is obtained from the solution by the addition of sodium chloride; and methanol;.
3.5 Produe Method
An alternative route for dithionite production is the reduction of sodium bisulfite with sodium borohydride. Sodium borohydride is obtained by reacting boron trimethyl ester, B(OCH3)3, with sodium hydride, NaH. The resulting product is hydrolyzed with water, and methanol is evaporated. An alkaline, aqueous solution is obtained, containing about 12% NaBH4 and 40% NaOH. This solution is commercially available. Reaction to dithionite is made on-site by adding sulfur dioxide and some additional caustic soda. Storages, handling and mixing of sulfur dioxide and of the Borol® liquid are not everywhere cost competitive.NaBH4+8NaOH+8SO2 → 4Na2S2O4+NaBO2+6H2O.
3.6 Usage
Sodium dithionite is a strong reducing agent and is produced commercially for use in vat dyeing.
4. Safety and Handling
4.1 Symbol
4.1 Hazard Codes
4.1 Signal Word
4.1 Risk Statements
4.1 Safety Statements
4.1 Packing Group
4.1 Octanol/Water Partition Coefficient
log Kow = < -4.7
4.2 Fire Hazard
Flammable/combustible material. May ignite on contact with moist air or moisture. May burn rapidly with flare-burning effect. Some react vigorously or explosively on contact with water. Some may decompose explosively when heated or involved in a fire. May re-ignite after fire is extinguished. Runoff may create fire or explosion hazard. Containers may explode when heated.
4.3 Other Preventative Measures
If material not on fire and not involved in fire: Do not use water. Keep sparks, flames, and other sources of ignition away. Keep material out of water sources and sewers. Keep material dry. /Sodium dithionite/
Hygiene measures: Handle in accordance with good industrial hygiene and safety practice. Wash hands before breaks and at the end of workday.
In case of skin contact: wash off with soap and plenty of water. Consult a physician.
In case of eye contact: rinse thoroughly with plenty of water for at least 15 minutes and consult a physician.
4.4 Hazard Class
4.4 Hazard Declaration
H251; H302
4.4 Cleanup Methods
Keep water away from release. Prompt cleanup and removal are necessary. Control runoff and isolate discharged material for proper disposal.
Personal precautions: Wear respiratory protection. Avoid dust formation. Avoid breathing dust. Ensure adequate ventilation.
Methods for cleaning up: Pick up and arrange disposal without creating dust. Keep in suitable, closed containers for disposal.
SRP: Wastewater from contaminant suppression, cleaning of protective clothing/equipment, or contaminated sites should be contained and evaluated for subject chemical or decomposition product concentrations. Concentrations shall be lower than applicable environmental discharge or disposal criteria. Alternatively, pretreatment and/or discharge to a permitted wastewater treatment facility is acceptable only after review by the governing authority and assurance that "pass through" violations will not occur. Due consideration shall be given to remediation worker exposure (inhalation, dermal and ingestion) as well as fate during treatment, transfer and disposal. If it is not practicable to manage the chemical in this fashion, it must be evaluated in accordance with EPA 40 CFR Part 261, specifically Subpart B, in order to determine the appropriate local, state and federal requirements for disposal.
4.5 DisposalMethods
Dissolve or mix the material with a combustible solvent and burn in a chemical incinerator equipped with an afterburner and scrubber. Observe all federal, state, and local environmental regulations. Contact a licensed professional waste disposal service to dispose of this material.
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.
4.6 DOT Emergency Guidelines
If ... THERE IS NO FIRE, go directly to the Table of Initial Isolation and Protective Action Distances /(see table below)/ ... to obtain initial isolation and protective action distances. IF THERE IS A FIRE, or IF A FIRE IS INVOLVED, go directly to the appropriate guide /(see guide(s) below)/ and use the evacuation information shown under PUBLIC SAFETY. /Sodium hydrosulfite (when spilled in water)/ Table of Initial Isolation and Protective Action Distances for Sodium hydrosulfite (when spilled in water) Small Spills (from a small package or small leak from a large package) -------------------- First ISOLATE in all Directions 30 meters (100 feet) Then PROTECT persons Downwind during DAY: 0.1 kilometers (0.1 miles) Then PROTECT persons Downwind during NIGHT: 0.2 kilometers (0.1 miles) ==================== Large Spills (from a large package or from many small packages) -------------------- First ISOLATE in all Directions 30 meters (100 feet) Then PROTECT persons Downwind during DAY: 0.3 kilometers (0.2 miles) Then PROTECT persons Downwind during NIGHT: 1.2 kilometers (0.7 miles)
Table of Water-Reactive Materials Which Produce Toxic Gases Materials Which Produce Large Amounts of Toxic-by-Inhalation (TIH) Gas(es) When Spilled in Water Name of Material TIH Gas(es) Produced Sodium hydrosulfite Hydrogen sulfide (H2S); Sulfur dioxide (SO2)
/GUIDE 135: SUBSTANCES - SPONTANEOUSLY COMBUSTIBLE/ Fire or Explosion: Flammable/combustible material. May ignite on contact with moist air or moisture. May burn rapidly with flare-burning effect. Some react vigorously or explosively on contact with water. Some may decompose explosively when heated or involved in a fire. May re-ignite after fire is extinguished. Runoff may create fire or explosion hazard. Containers may explode when heated.
/GUIDE 135: SUBSTANCES - SPONTANEOUSLY COMBUSTIBLE/ Health: Fire will produce irritating, corrosive and/or toxic gases. Inhalation of decomposition products may cause severe injury or death. Contact with substance may cause severe burns to skin and eyes. Runoff from fire control may cause pollution.
/GUIDE 135: SUBSTANCES - SPONTANEOUSLY COMBUSTIBLE/ Public Safety: CALL Emergency Response Telephone Number ... As an 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. Stay upwind. Keep unauthorized personnel away. Keep out of low areas.
/GUIDE 135: SUBSTANCES - SPONTANEOUSLY COMBUSTIBLE/ Protective Clothing: Wear positive pressure self-contained breathing apparatus (SCBA). Wear chemical protective clothing that is specifically recommended by the manufacturer. It may provide little or no thermal protection. Structural firefighters' protective clothing will only provide limited protection.
/GUIDE 135: SUBSTANCES - SPONTANEOUSLY COMBUSTIBLE/ Evacuation: ... Fire: If tank, rail car or tank truck 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.
/GUIDE 135: SUBSTANCES - SPONTANEOUSLY COMBUSTIBLE/ Fire: DO NOT USE WATER, CO2 OR FOAM ON MATERIAL ITSELF. Some of these materials may react violently with water. ... Small fires: Dry chemical, soda ash, lime or dry sand. ... Large fires: DRY sand, dry chemical, soda ash or lime, ... or withdraw from area and let fire burn. Move containers from fire area if you can do it without risk. Fire involving tanks or car/trailer loads: Fight fire from maximum distance or use unmanned hose holders or monitor nozzles. Do not get water inside containers or in contact with substance. Cool containers with flooding quantities of water until well after fire is out. Withdraw immediately in case of rising sound from venting safety devices or discoloration of tank. ALWAYS stay away from tanks engulfed in fire.
/GUIDE 135: SUBSTANCES - SPONTANEOUSLY COMBUSTIBLE/ Spill or Leak: Fully encapsulating, vapor protective clothing should be worn for spills and leak with no fire. ELIMINATE all ignition sources (no smoking, flares, sparks or flames in immediate area). Do not touch or walk through spilled material. Stop leak if you can do it without risk. Small spills: ... Cover with DRY earth, DRY sand, or other non-combustible material followed with plastic sheet to minimize spreading or contact with rain. Use clean non-sparking tools to collect material and place it into loosely covered plastic containers for later disposal. Prevent entry into waterways, sewers, basements or confined areas.
/GUIDE 135: SUBSTANCES - SPONTANEOUSLY COMBUSTIBLE/ First Aid: Move victim to fresh air. Call 911 or emergency medical service. Give artificial respiration if victim is not breathing. Administer oxygen if breathing is difficult. Remove and isolate contaminated clothing and shoes. In case of contact with substance, immediately flush skin or eyes with running water for at least 20 minutes. Keep victim warm and quiet. Ensure that medical personnel are aware of the material(s) involved and take precautions to protect themselves.
UN 1384
4.7 Fire Fighting Procedures
Special protective equipment for fire-fighters: Wear self contained breathing apparatus for fire fighting if necessary.
Use only flooding quantities of water. Monitor temperature of containers exposed to fire for at least 48 hours to verify decomposition has not begun in the sealed container.
4.8 FirePotential
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.
Flammable when exposed to heat or flame. Ignites on contact with water or sodium chorite.
4.9 Safety Profile
Toxic and an irritant. An allergen. Flammable when exposed to heat or flame. Ignites on contact with water or sodium chlorite. To extinpsh fires, flood the reacting mass with water. Decomposes violently when heated to 19OOC and emits toxic fumes of SOx and NazO
4.10 Caution Statement
P301 + P312 + P330-P407-P413-P420
4.10 Formulations/Preparations
Commercial sodium dithionite generally has a purity of about 88%. It contains about 3% of each of the following: sodium disulfite, sodium sulfite, sodium sulfate, and sodium carbonate. The latter stabilizes the Na2S2O4. The total heavy metal content is generally
Grades: technical; reagent. /Dihydrate/
Hydrosulfite of commerce contains 85-90% Na2S2O4.
V-Brite B
Virtex CC
Virtex D
Virtex L
Virtex RD
4.11 WGK Germany
4.11 Protective Equipment and Clothing
Respiratory protection: Where risk assessment shows air-purifying respirators are appropriate use a dust mask type N95 (US) or type P1 (EN 143) respirator. Use respirators and components tested and approved under appropriate government standards such as NIOSH (US) or CEN (EU).
Hand protection: The selected protective gloves have to satisfy the specifications of EU Directive 89/686/EEC and the standard EN 374 derived from it. Handle with gloves.
Eye protection: Safety glasses with side-shields conforming to EN166.
Skin and body protection: Choose body protection according to the amount and concentration of the dangerous substance at the work place.
Wear full protective clothing and positive pressure self-contained breathing apparatus.
4.12 Reactivities and Incompatibilities
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.
Reacts on exposure to moist air to form toxic and corrosive fumes with generation of heat and risk of combustion. The substance is a strong reducing agent and reacts violently with oxidants. Upon contact with dry air the substance passes into a mixt of sodium bisulfate and sodium bisulfite. Reacts with acids to form sulfur oxides. /Dihydrate/
Reacts with oxidizing agents, acidic materials, moisture. Exposure to moisture either from humid air or from small amounts of water can result in spontaneous chemical reactions which may generate sufficient heat to initiate thermal decomposition. Heat above 50 deg C can also initiate thermal decomposition.
4.13 Report

Reported in EPA TSCA Inventory.

4.14 Skin, Eye, and Respiratory Irritations
Irritating to skin, eyes, and respiratory system.
4.15 Safety

Toxic and an irritant. An allergen. Flammable when exposed to heat or flame. Ignites on contact with water or sodium chlorite. To extinguish fires, flood the reacting mass with water. Decomposes violently when heated to 190°C and emits toxic fumes of SOx and Na2O.
Hazard Codes?: ?Xn
The Risk Statements information of?Sodium hydrosulfite (CAS NO.7775-14-6):
7:? May cause fire?
22:? Harmful if swallowed?
31:? Contact with acids liberates toxic gas?
The Safety Statements information of?Sodium hydrosulfite (CAS NO.7775-14-6):
26:? In case of contact with eyes, rinse immediately with plenty of water and seek medical advice?
28:? After contact with skin, wash immediately with plenty of ... (to be specified by the manufacturer)?
43:? In case of fire, use ... (indicate in the space the precise type of fire-fighting equipment. If water increases the risk add - Never use water)?
7/8:? Keep container tightly closed and dry???
RIDADR: UN 1384 4.2/PG 2
WGK Germany: 1
F: 1-10
HazardClass: 4.2
PackingGroup: II

4.16 Sensitive
Moisture Sensitive
4.17 Specification

First?aid measures?:
Eyes:Flush eyes with plenty of water for at least 15 minutes,occasionally lifting the upper and lower eyelids. Get medical aid immediately.
Skin:Get medical aid if irritation develops or persists. Wash clothing before reuse. Flush skin with plenty of soap and water.
Ingestion:Do not induce vomiting. If victim is conscious and alert, give 2-4 cupfuls of milk or water. Never give anything by mouth to an unconscious person. Get medical aid immediately.
Inhalation:Remove from exposure and move to fresh air immediately. If not breathing, give artificial respiration. If breathing is difficult,give oxygen. Get medical aid. Do NOT use mouth-to-mouth resuscitation.

4.18 Toxicity
LD50 orally in Rabbit: 2500 mg/kg

2.Hazard identification

2.1 Classification of the substance or mixture

Self- heating substances and mixtures, Category 1

Acute toxicity - Oral, Category 4

2.2 GHS label elements, including precautionary statements

Signal word


Hazard statement(s)

H251 Self-heating; may catch fire

H302 Harmful if swallowed

Precautionary statement(s)

P235 Keep cool.

P280 Wear protective gloves/protective clothing/eye protection/face protection.

P264 Wash ... thoroughly after handling.

P270 Do not eat, drink or smoke when using this product.


P301+P312 IF SWALLOWED: Call a POISON CENTER/doctor/\u2026if you feel unwell.

P330 Rinse mouth.


P407 Maintain air gap between stacks or pallets.

P413 Store bulk masses greater than \u2026 kg/\u2026lbs at temperatures not exceeding \u2026\u00b0C/\u2026\u00b0F.

P420 Store separately.


P501 Dispose of contents/container to ...

2.3 Other hazards which do not result in classification


6. NMR Spectrum
7. Other Information
7.0 Usage
Sodium hydrosulfite is used as a reducing agent in aqueous solutions, sulfonating agent , chelating agent and decolorizing agent in organic reactions. It finds application in water treatment, gas purification, cleaning, leather, polymers, photography, and many others. It is involved in chemical enhanced oil recovery to stabilize polyacrylamide polymers against radical degradation in the presence of iron. It plays an important role to determine the iron content in soil chemistry.
8. Computational chemical data
  • Molecular Weight: 174.096g/mol
  • Molecular Formula: Na2O4S2
  • Compound Is Canonicalized: True
  • XLogP3-AA: null
  • Exact Mass: 173.90333939
  • Monoisotopic Mass: 173.90333939
  • Complexity: 60.5
  • Rotatable Bond Count: 0
  • Hydrogen Bond Donor Count: 0
  • Hydrogen Bond Acceptor Count: 6
  • Topological Polar Surface Area: 119
  • Heavy Atom Count: 8
  • Defined Atom Stereocenter Count: 0
  • Undefined Atom Stereocenter Count: 0
  • Defined Bond Stereocenter Count: 0
  • Undefined Bond Stereocenter Count: 0
  • Isotope Atom Count: 0
  • Covalently-Bonded Unit Count: 3
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