Sodium hydrosulfite (Na2S2O4) is a white crystalline powder used as a reducing agent in various industries such as textiles and paper. It removes color from fabrics and paper pulp.
| IUPAC Name | Sodium dithionite |
| Molecular Formula | Na2S2O4 |
| CAS Number | 7775-14-6 |
| Synonyms | Sodium hyposulfite, Sodium dithionate, Sodium sulfoxylate, Sodium hydrogen sulfite |
| InChI | InChI=1S/2Na.H2O4S2/c;;1-5(2,3)4/h;;(H2,1,2,3,4)/q2*+1;/p-2 |
Sodium Hydrosulfite Properties
Sodium Hydrosulfite Formula
The chemical formula for Sodium Hydrosulfite is Na2S2O4. This means that each molecule of Sodium Hydrosulfite contains two atoms of sodium, two atoms of sulfur, and four atoms of oxygen. The formula indicates that the compound is made up of positively charged sodium ions and negatively charged sulfite ions.
Sodium Hydrosulfite Molar Mass
The molar mass of Na2S2O4 is 174.11 g/mol. This value is calculated by adding the atomic masses of the elements present in one molecule of Na2S2O4. The molar mass is an important parameter in stoichiometry and is used to calculate the amount of substance in a given sample of the compound.
Sodium Hydrosulfite Boiling Point
Na2S2O4 is a stable compound and does not have a boiling point. Instead, it decomposes when heated above 150°C to release sulfur dioxide gas and water vapor. The decomposition reaction is exothermic, and caution should be taken when heating Na2S2O4.
Sodium Hydrosulfite Melting Point
The melting point of Na2S2O4 is 300°C. At this temperature, the solid compound melts to form a colorless liquid. The melting point is an important parameter for determining the stability of the compound and its suitability for different applications.
Sodium Hydrosulfite Density g/ml
The density of Na2S2O4 is 1.48 g/ml. This value indicates that Na2S2O4 is a relatively dense compound compared to water. The density is an important parameter for determining the solubility of the compound and its ability to mix with other substances.
Sodium Hydrosulfite Molecular Weight
The molecular weight of Na2S2O4 is 174.11 g/mol. This value is calculated by adding the atomic masses of the elements present in one molecule of Na2S2O4. The molecular weight is an important parameter for determining the amount of substance in a given sample of the compound.
Sodium Hydrosulfite Structure
The structure of Na2S2O4 is tetrahedral, with the sulfur atoms at the corners of the tetrahedron and the oxygen atoms forming the edges. The sodium ions are located in the center of the tetrahedron. The structure of Na2S2O4 is important for understanding its chemical and physical properties.
Sodium Hydrosulfite Solubility
Na2S2O4 is highly soluble in water, with a solubility of 58 g/100 mL at 20°C. The solubility is affected by temperature and pH, with higher solubility observed at higher temperatures and lower pH values. The high solubility of Na2S2O4 makes it useful in various applications such as textile and paper industries where it is used as a reducing agent.
| Appearance | White crystalline powder |
| Specific Gravity | 1.48 |
| Color | Colorless |
| Odor | Odorless |
| Molar Mass | 174.11 g/mol |
| Density | 1.48 g/mL |
| Melting Point | 300 °C |
| Boiling Point | Decomposes at 150 °C |
| Flash Point | Not applicable |
| Water Solubility | Highly soluble |
| Solubility | Soluble in water, glycerol, ethanol |
| Vapour Pressure | Not applicable |
| Vapour Density | Not applicable |
| pKa | 6.6 |
| pH | 7-8 (1% solution) |
Sodium Hydrosulfite Safety and Hazards
Na2S2O4 is generally safe when handled and used properly, but it can pose some hazards if mishandled or improperly used. It is classified as a hazardous substance, and it can cause skin and eye irritation if it comes into contact with these parts of the body. Inhaling the dust or mist of Na2S2O4 can also irritate the respiratory system. Na2S2O4 is also a reducing agent, which means it can react with other chemicals and produce flammable or explosive gases. Proper safety measures, such as wearing protective equipment and handling the substance in well-ventilated areas, should be observed to prevent accidents and injuries.
| Hazard Symbols | Xi, C |
| Safety Description | Avoid contact with skin and eyes. Do not inhale dust or mist. Wear protective equipment. Handle in well-ventilated areas. |
| UN IDs | UN1384 |
| HS Code | 28311000 |
| Hazard Class | 4.2 |
| Packing Group | III |
| Toxicity | LD50: 1520 mg/kg (oral, rat); LC50: 1840 ppm/4h (inhalation, rat) |
Sodium Hydrosulfite Synthesis Methods
Several methods can synthesize Na2S2O4, but the most common ones involve sodium bisulfite and sodium dithionite reacting with each other.
One method involves adding sodium bisulfite to a solution of sodium hydroxide and sodium dithionite, while another method involves heating a mixture of sodium bisulfite and sodium dithionite.
The formation of Na2S2O4 yields a white crystalline powder that one can collect and purify in both methods.
Another method for synthesizing Na2S2O4 involves the reaction between sulfur dioxide and sodium borohydride. The reaction produces Na2S2O4 along with sodium borate and hydrogen gas. This method is generally less common than the sodium bisulfite and sodium dithionite methods.
Sodium Hydrosulfite Uses
Na2S2O4 has a variety of uses across different industries due to its unique properties. Here are some of its uses:
- Textile Industry: Used as a reducing agent in the textile industry to remove excess dye and bleach fabrics.
- Paper Industry: Used in the paper industry to bleach wood pulp and paper products.
- Food Industry: Used as a food additive to prevent discoloration and as a preservative in canned fruits and vegetables.
- Water Treatment: Used to remove excess chlorine in drinking water and wastewater treatment.
- Mining Industry: Used in the mining industry to separate copper and molybdenum ores.
- Polymer Industry: Used in the polymer industry to reduce the color of polymers and plastics.
- Photography Industry: Used in the photography industry as a photographic fixer to remove unexposed silver halides from photographic prints.
- Other Industrial Applications: Used in various other industries, such as leather processing, oil drilling, and as a reducing agent in chemical synthesis reactions.
Questions:
Q: What cleaner has sodium hydrosulfite?
A: Na2S2O4 is commonly used in household cleaners for removing stains and as a bleach alternative.
Q: What is the function of sodium hydrosulfite in the reaction with indigo?
A: Na2S2O4 acts as a reducing agent in the reaction with indigo, which converts the insoluble blue indigo dye into a soluble, colorless compound.
Q: Where to buy sodium hydrosulfite?
A: Na2S2O4 can be purchased from chemical suppliers, such as Sigma-Aldrich, Fisher Scientific, and VWR International.
Q: How to neutralize sodium hydrosulfite?
A: Na2S2O4 can be neutralized with sodium hydroxide or another strong base.
Q: What Indian foods use sodium hydrosulfite?
A: Na2S2O4 is not commonly used in Indian foods.
Q: How does sodium hydrosulfite bleach?
A: Na2S2O4 acts as a reducing agent and breaks down the chemical bonds that give color to the material, thus removing the color and resulting in bleaching.
Q: What is the function of sodium hydrosulfite in the reaction with indigo?
A: Na2S2O4 acts as a reducing agent in the reaction with indigo, which converts the insoluble blue indigo dye into a soluble, colorless compound.
Q: What produces odor when adding sodium hydrosulfite?
A: When adding Na2S2O4, it can produce a sulfur-like odor due to the release of sulfur dioxide gas.
Q: Is sodium hydrosulfite dihydrate a reducing agent?
A: Yes, Na2S2O4 dihydrate is a powerful reducing agent that is commonly used in industrial processes.