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Sodium dithionite is a whitish to light yellow crystalline solid having a sulfur dioxide-like odor.
Sodium dithionite is a powerful reducing agent.
Sodium dithionite has therefore been suggested to be used as an additive in kraft pulping to improve the yield.
CAS Number: 7775-14-6
EC Number: 231-890-0
Chemical Formula: Na2S2O4
Molar Mass: 174.11 g/mol
Sodium dithionite (also known as sodium hydrosulfite) is a white crystalline powder with a sulfurous odor.
Although Sodium dithionite is stable in dry air, Sodium dithionite decomposes in hot water and in acid solutions.
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.
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.
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.
Under prolonged exposure to fire or intense heat containers of this material may violently rupture.
Sodium dithionite is used in dyeing and to bleach paper pulp.
Sodium dithionite is an inorganic sodium salt that is the disodium salt of dithionous acid.
Sodium dithionite has a role as a reducing agent and a bleaching agent.
Sodium dithionite contains a dithionite(2-).
The dithionous acid ion and Sodium dithionite salts.
Sodium dithionite is also called sodium hydrosulfite, sodium sulfoxylate and sulfoxylate.
Sodium dithionite is unstable under physiological conditions, Sodium dithionite degradation rate increases with increasing acidity.
After contact with moisture, Sodium dithionite is oxidized to hydrogen sulfide (hso3-), sulfite (so32-), and hydrogen sulfate (hso4-).
Sodium dithionite can release sulfur dioxide under strongly acidic conditions.
Under anaerobic conditions (as in the lower gastrointestinal tract), hydrogen sulfide (hso3-) and thiosulfate (s2o32-) can occur.
Hydrogen sulfide (hso3-) can be absorbed after ingestion.
Sodium dithionite is metabolized efficiently and most of Sodium dithionite is rapidly excreted as sulfate in the urine.
Sodium hydrosulfite is widely used in industry due to Sodium dithionite reducing properties and ability to react with oxygen.
Sodium dithionite is used as a reducing bleaching agent to make yellow discoloration of cellulose-based products in the textile industry, in the pulp and paper industry as a reducing bleach, as an oxygen scavenger in boilers, for preservation and water treatment to remove iron stains on cultural artifacts.
Iron flash control on white fabrics in bleaching environments.
Sodium dithionite is also used in photographic film, clay, wine, leather goods, food and beverages, polymers, cleaners, gas cleaning, environmental remediation, metal recovery and chemical processing.
Sodium dithionite (Na2S2O4) is a powerful reducing agent.
Sodium dithionite has therefore been suggested to be used as an additive in kraft pulping to improve the yield.
However, sodium dithionite easily decomposes and Sodium dithionite is thus important to determine the effect of different conditions.
The stability of sodium dithionite was found to decrease with increasing heating temperature, concentration of sodium dithionite, heating time and pH.
Sodium dithionite was found to be relatively stable at moderate alkaline pH: 11.5 and 12.5, while a rapid decrease in stability with time was noted at higher heating temperatures and concentrations of sodium dithionite.
Based on this study on the thermal stability of sodium dithionite, the following conditions are suggested as the most promising, when adding sodium dithionite to the kraft cooking as an additive; pH 12.5, with 0.4 M concentration of the solution, at a heating temperature of 100 °C.
Uses of Sodium dithionite:
Sodium dithionite is used to dye fibers and textiles, to strip dyes from fabrics, and to bleach sugar, soap, oils and wood pulp.
Sodium dithionite is used as a chemical reagent and an oxygen scavenger in the production of synthetic rubber.
All uses of sodium dithionite are based on Sodium dithionite reducing properties.
In the textile industry, sodium dithionite is primarily used as reducing agent for vat dyes and sulfur containing dyes, and for the removal of pigments on textiles.
Sodium dithionite is also used as a bleaching agent in reductive bleaching processes, for instance, in the bleaching of mechanical paper pulp, and the bleaching of cotton and wool, as well as sugar.
Industry Uses:
Bleaching agent
Bleaching agents
Cleaning agent
Dye
Not Known or Reasonably Ascertainable
Other (specify)
Oxidizing/reducing agents
Reducing agent
Solvents (which become part of product formulation or mixture)
Consumer Uses:
Not Known or Reasonably Ascertainable
Reducing agent
Usage Areas of Sodium dithionite:
In the textile sector, Sodium dithionite provides a reductive reaction with the dye remaining on the fiber after dyeing, allowing excess dye to be removed from the fiber.
Sodium dithionite is used in the paper industry for bleaching pulp.
Sodium dithionite is used in the food industry to bleach sherbet and maltose.
Sulfonation in water treatment, bleaching of minerals by removing iron ions, production of chemicals
Industrial Processes with risk of exposure:
Pulp and Paper Processing
Textiles (Printing, Dyeing, or Finishing)
Toxic Gas from Spilling Chemical in Water
Applications of Sodium dithionite:
Industry:
Being water-soluble, sodium dithionite is used as a reducing agent in some industrial dyeing processes.
In the case of sulfur dyes and vat dyes, an otherwise water-insoluble dye can be reduced into a water-soluble alkali metal salt (e.g. indigo dye).
Sodium dithionite can also be used for water treatment, aquarium water conditioners, gas purification, cleaning, and stripping.
Sodium dithionite has also been applied as a sulfonating agent.
In addition to the textile industry, this compound is used in industries concerned with leather, foods, polymers, photography, and many others, often as a decolourising agent.
Sodium dithionite is even used domestically as a decoloring agent for white laundry, when Sodium dithionite has been accidentally stained by way of a dyed item slipping into the high temperature washing cycle.
Sodium dithionite is usually available in 5 gram sachets termed hydrosulfite after the antiquated name of the salt.
Sodium dithionite is the an active ingredient in "Iron Out Rust Stain Remover", a commercial rust product.
Laboratory:
Sodium dithionite is often used in physiology experiments as a means of lowering solutions' redox potential (Eo' -0.66 V vs SHE at pH 7).
Potassium ferricyanide is usually used as an oxidizing chemical in such experiments (Eo' ~ .436 V at pH 7).
In addition, sodium dithionite is often used in soil chemistry experiments to determine the amount of iron that is not incorporated in primary silicate minerals.
Hence, iron extracted by sodium dithionite is also referred to as "free iron."
The strong affinity of the dithionite ion for bi- and trivalent metal cations (M2+, M3+) allows Sodium dithionite to enhance the solubility of iron, and therefore dithionite is a useful chelating agent.
Aqueous solutions of sodium dithionite were once used to produce 'Fieser's solution' for the removal of oxygen from a gas stream.
Pyrithione can be prepared in a two-step synthesis from 2-bromopyridine by oxidation to the N-oxide with a suitable peracid followed by substitution using sodium dithionite to introduce the thiol functional group.
Photography:
Sodium dithionite is used in Kodak fogging developer, FD-70.
This is used in the second step in processing black and white positive images, for making slides.
Sodium dithionite is part of the Kodak Direct Positive Film Developing Outfit.
Preparation of Sodium dithionite:
Sodium dithionite is produced industrially by reduction of sulfur dioxide.
Approximately 300,000 tons were produced in 1990.
The route using zinc powder is a two-step process:
2 SO2 + Zn → ZnS2O4
ZnS2O4 + 2 NaOH → Na2S2O4 + Zn(OH)2
The sodium borohydride method obeys the following stoichiometry:
NaBH4 + 8 NaOH + 8 SO2 → 4 Na2S2O4 + NaBO2 + 6 H2O
Each equivalent of H− reduces two equivalents of sulfur dioxide.
Formate has also been used as the reductant.
Structure of Sodium dithionite:
The structure has been examined by Raman spectroscopy and single-crystal X-ray diffraction.
The dithionite dianion has C2 symmetry, with almost eclipsed with a 16° O-S-S-O torsional angle.
In the dihydrated form (Na2S2O4·2H2O), the dithionite anion has gauche 56° O-S-S-O torsional angle.
A weak S-S bond is indicated by the S-S distance of 239 pm, which is elongated by ca. 30 pm relative to a typical S-S bond.
Because this bond is fragile, the dithionite anion dissociates in solution into the [SO2]− radicals, as has been confirmed by EPR spectroscopy.
Sodium dithionite is also observed that 35S undergoes rapid exchange between S2O42− and SO2 in neutral or acidic solution, consistent with the weak S-S bond in the anion.
Properties and Reactions of Sodium dithionite:
Hydrolysis:
Sodium dithionite is stable when dry, but aqueous solutions deteriorate due to the following reaction:
2 S2O42− + H2O → S2O32− + 2 HSO3−
This behavior is consistent with the instability of dithionous acid.
Thus, solutions of sodium dithionite cannot be stored for a long period of time.
Anhydrous sodium dithionite decomposes to sodium sulfate and sulfur dioxide above 90 °C in the air.
In absence of air, Sodium dithionite decomposes quickly above 150 °C to sodium sulfite, sodium thiosulfate, sulfur dioxide and trace amount of sulfur.
Redox reactions of Sodium dithionite:
Sodium dithionite is a reducing agent.
At pH 7, the potential is -0.66 V compared to the normal hydrogen electrode.
Redox occurs with formation of bisulfite:
S2O42- + 2 H2O → 2 HSO3− + 2 e− + 2 H+
Sodium dithionite reacts with oxygen:
Na2S2O4 + O2 + H2O → NaHSO4 + NaHSO3
These reactions exhibit complex pH-dependent equilibria involving bisulfite, thiosulfate, and sulfur dioxide.
With organic carbonyls:
In the presence of aldehydes, sodium dithionite reacts either to form α-hydroxy-sulfinates at room temperature or to reduce the aldehyde to the corresponding alcohol above a temperature of 85 °C.
Some ketones are also reduced under similar conditions.
Manufacturing Methods of Sodium dithionite:
Zinc dust process:
An aqueous slurry of zinc dust is treated in a stirred reactor with cooling at ca. 40 °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 °C.
Sodium dithionite is filtered, washed with methanol, and dried at 90 - 100 °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.
Amalgam Process:
In the amalgam process, sodium hydrogensulfite is reduced to sodium dithionite in aqueous solution in a cooled, stirred vessel using the sodium amalgam of a chloralkali electrolysis cell.
The sodium-free mercury is returned to the electrolysis cell where Sodium dithionite is recharged with sodium.
During reaction of the amalgam with the hydrogensulfite solution a pH of 5 - 6 must be maintained.
Sodium dithionite is obtained by precipitation with salts or methanol or both.
Formate Process:
Sodium formate, dissolved in 80% aqueous methanol, is charged to a stirred vessel.
At a pressure of 2 - 3 bar sulfur dioxide and sodium hydroxide are introduced into this solution such that a pH of 4 - 5 is maintained.
Sodium Borohydride Process Sodium borohydride is stable in strong aqueous alkali and can be used in this form for the production of sodium dithionite by adding SO2 and sodium hydroxide.
Reactivity Profile of Sodium dithionite:
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 Sodium dithionite slowly oxidizes, generating toxic sulfur dioxide gas.
Handling and Storage of Sodium dithionite:
Nonfire Spill Response:
ELIMINATE all ignition sources (no smoking, flares, sparks or flames) from immediate area.
Do not touch or walk through spilled material.
Stop leak if you can do it without risk.
SMALL SPILL:
For spills of Xanthates, UN3342 and for Dithionite (Hydrosulfite/Hydrosulphite), UN1384, UN1923 and UN1929, dissolve in 5 parts water and collect for proper disposal.
CAUTION:
UN3342 when flooded with water will continue to evolve flammable Carbon disulfide/Carbon disulphide vapors.
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 Sodium dithionite into loosely covered plastic containers for later disposal.
Prevent entry into waterways, sewers, basements or confined areas.
Safe Storage:
Separated from strong oxidants and acids.
Store in an area without drain or sewer access.
Storage Conditions:
Store in cool place.
Keep container tightly closed in a dry and well-ventilated place.
Do not store near acids.
Handle under inert gas.
Protect from moisture.
Store in a cool, dry, well-ventilated location.
Outside or detached storage is preferred.
Separate from combustibles and oxiding materials.
Immediately remove and properly dispose of any spilled material.
Materials to avoid:
Strong oxidizing agents, acids.
First Aid Measures of Sodium dithionite:
Call 911 or emergency medical service.
Ensure that medical personnel are aware of Sodium dithionite(s) involved and take precautions to protect themselves.
Move victim to fresh air if Sodium dithionite can be done safely.
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 calm and warm.
Fire Fighting of Sodium dithionite:
DO NOT USE WATER, CO2 OR FOAM ON MATERIAL ITSELF.
Some of these materials may react violently with water.
CAUTION:
For Xanthates, UN3342 and for Dithionite (Hydrosulfite/Hydrosulphite) UN1384, UN1923 and UN1929, USE FLOODING AMOUNTS OF WATER for SMALL AND LARGE fires to stop the reaction.
Smothering will not work for these materials, they do not need air to burn.
SMALL FIRE:
Dry chemical, soda ash, lime or DRY sand, EXCEPT for UN1384, UN1923, UN1929 and UN3342.
LARGE FIRE:
DRY sand, dry chemical, soda ash or lime EXCEPT for UN1384, UN1923, UN1929 and UN3342, or withdraw from area and let fire burn.
CAUTION:
UN3342 when flooded with water will continue to evolve flammable Carbon disulfide/Carbon disulphide vapors.
If Sodium dithionite can be done safely, move undamaged containers away from the area around the fire.
FIRE INVOLVING TANKS OR CAR/TRAILER LOADS:
Fight fire from maximum distance or use unmanned master stream devices 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.
Accidental Release Measures of Sodium dithionite:
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:
Initial Isolation and Protective Action Distances on the UN/NA 1384 datasheet.
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.
Spillage Disposal of Sodium dithionite:
Personal protection:
Particulate filter respirator adapted to the airborne concentration of Sodium dithionite.
Do NOT let this chemical enter the environment.
Sweep spilled substance into covered containers.
Carefully collect remainder.
Then store and dispose of according to local regulations.
Do NOT absorb in saw-dust or other combustible absorbents.
Identifiers of Sodium dithionite:
CAS Number: 7775-14-6
ChEBI: CHEBI:66870
ChemSpider: 22897
ECHA InfoCard: 100.028.991
EC Number: 231-890-0
PubChem CID: 24489
RTECS number: JP2100000
UNII: 2K5B8F6ES1
UN number: 1384
CompTox Dashboard (EPA): DTXSID9029697
InChI: InChI=1S/2Na.H2O4S2/c;;1-5(2)6(3)4/h;;(H,1,2)(H,3,4)/q2*+1;/p-2
Key: JVBXVOWTABLYPX-UHFFFAOYSA-L
SMILES: [O-]S(=O)S(=O)[O-].[Na+].[Na+]
Linear Formula: Na2S2O4
MDL Number: MFCD00011640
EC No.: 231-890-0
Beilstein/Reaxys No.: N/A
Pubchem CID: 24489
IUPAC Name: N/A
SMILES: [O-]S(=O)S(=O)[O-].[Na+].[Na+]
InchI Identifier: InChI=1S/2Na.H2O4S2/c;;1-5(2)6(3)4/h;;(H,1,2)(H,3,4)/q2*+1;/p-2
InchI Key: JVBXVOWTABLYPX-UHFFFAOYSA-L
CAS number: 7775-14-6
EC index number: 016-028-00-1
EC number: 231-890-0
Hill Formula: Na₂O₄S₂
Chemical formula: Na₂S₂O₄
Molar Mass: 174.11 g/mol
HS Code: 2831 10 00
Quality Level: MQ200
CAS: 7775-14-6
Molecular Formula: Na2O4S2
Molecular Weight (g/mol): 174.096
MDL Number: 11640
InChI Key: JVBXVOWTABLYPX-UHFFFAOYSA-L
PubChem CID: 24489
ChEBI: CHEBI:66870
SMILES: [O-]S(=O)S(=O)[O-].[Na+].[Na+]
Properties of Sodium dithionite:
Chemical formula: Na2S2O4
Molar mass: 174.107 g/mol (anhydrous)
210.146 g/mol (dihydrate)
Appearance: white to grayish crystalline powder
light-lemon colored flakes
Odor: faint sulfur odor
Density: 2.38 g/cm3 (anhydrous)
1.58 g/cm3 (dihydrate)
Melting point: 52 °C (126 °F; 325 K)
Boiling point: Decomposes
Solubility in water: 18.2 g/100 mL (anhydrous, 20 °C)
21.9 g/100 mL (Dihydrate, 20 °C)
Solubility: slightly soluble in alcohol
Density: 2.5 g/cm3 (20 °C)
Flash point: >100 °C
Ignition temperature: >200 °C
Melting Point: 100 °C (decomposition)
pH value: 5.5 - 8.5 (50 g/l, H₂O, 20 °C)
Bulk density: 1250 kg/m3
Solubility: 250 g/l (slow decomposition)
Compound Formula: Na2O4S2
Molecular Weight: 174.107
Appearance: White crystalline powder
Melting Point: 52 °C
Boiling Point: Decomposes
Density: 2.8 g/cm3
Solubility in H2O: 18.2 g/100 mL (20 °C)
Exact Mass: 173.903339
Monoisotopic Mass: 173.903339
Molecular Weight: 174.11 g/mol
Hydrogen Bond Donor Count: 0
Hydrogen Bond Acceptor Count: 6
Rotatable Bond Count: 0
Exact Mass: 173.90333939 g/mol
Monoisotopic Mass: 173.90333939 g/mol
Topological Polar Surface Area: 119Ų
Heavy Atom Count: 8
Complexity: 60.5
Isotope Atom Count: 0
Defined Atom Stereocenter Count: 0
Undefined Atom Stereocenter Count: 0
Defined Bond Stereocenter Count: 0
Undefined Bond Stereocenter Count: 0
Covalently-Bonded Unit Count: 3
Compound Is Canonicalized: Yes
Specifications of Sodium dithionite:
Assay (iodometric): ≥ 85.0 %
Identity: passes test
Chloride (Cl): ≤ 0.05 %
Fe (Iron): ≤ 0.005 %
Melting Point: 300°C
Color: White
pH: 8 to 9.5
Physical Form: Powder/Solid
Quantity: 500 g
Formula Weight: 174.1g/mol
Packaging: Plastic powder jar
Related compounds of Sodium dithionite:
Sodium thiosulfate
Sodium bisulfite
Sodium metabisulfite
Sodium bisulfate
Other anions:
Sodium sulfite
Sodium sulfate
Names of Sodium dithionite:
D-Ox, Hydrolin, Reductone
sodium hydrosulfite, sodium sulfoxylate, Sulfoxylate
Vatrolite, Virtex L
Hydrosulfit, Prayon
Blankit, Albite A, Konite
Zepar, Burmol, Arostit
Synonyms of Sodium dithionite:
Sodium dithionite
SODIUM HYDROSULFITE
7775-14-6
Sodium hydrosulphite
Dithionous acid, disodium salt
Sodium sulfoxylate
Disodium dithionite
Sodium hypodisulfite
Vatrolite
2K5B8F6ES1
CHEBI:66870
Blankit
Burmol
Hydros
sodiumdithionite
Blankit IN
Hydrosulfite R Conc
V-Brite B
Disodium hydrosulfite
Caswell No. 774
CCRIS 1428
HSDB 746
Sodium hydrosulfite (Na2S2O4)
Sodium dithionite (Na2(S2O4))
EINECS 231-890-0
UN1384
EPA Pesticide Chemical Code 078202
UNII-2K5B8F6ES1
sodium dithionit
sodiumhydrosulfite
Sodiumhydrosulphite
sodium hydro sulfite
MFCD00011640
sodium sodium hydrosulfite
Dithionous aciddisodiuMsalt
Na2S2O4
EC 231-890-0
Sodium dithionite (Na2S2O4)
SODIUM DITHIONITE [II]
SODIUM DITHIONITE [MI]
CHEMBL3410462
DTXSID9029697
Na2 (S2 O4)
SODIUM DITHIONITE [MART.]
SODIUM HYDROSULFITE [HSDB]
SODIUM HYDROSULFITE [INCI]
Dithionous acid, sodium salt (1:2)
AKOS015904498
Sodium dithionite or sodium hydrosulfite
BP-13393
FT-0695294
S0562
Q414560
Sodium dithionite or sodium hydrosulfite [UN1384] [Spontaneously combustible]
Sodium dithionite [Wiki]
14844-07-6 [RN]
231-890-0 [EINECS]
2K5B8F6ES1
7775-14-6 [RN]
Dinatriumdithionit [German] [ACD/IUPAC Name]
Disodium dithionite [ACD/IUPAC Name]
Dithionite [ACD/IUPAC Name]
Dithionite de disodium [French] [ACD/IUPAC Name]
Dithionous acid, disodium salt
MFCD00011640 [MDL number]
Sodium hydrosulfite
Sodium hydrosulphite
Sodium hypodisulfite
1340-77-8 [RN]
Blankit
Burmol
Disodium hydrosulfite
disodium sulfinatosulfinate
Dithionous aciddisodiumsalt
EINECS 231-890-0
SODIUM DITHIONATE
Sodium dithionite (Na2S2O4)
Sodium Hydrosulfite, 85per cent
Sodium hydrosulfite, Sodium hypodisulfite
Sodium hyposulfite
Sodium sulfoxylate
sodiumdithionite
UNII:2K5B8F6ES1
UNII-2K5B8F6ES1
Vatrolite
V-Brite B
