Sodium Bisulphite

Sodium bisulphite is widely used in almost all commercial wines to prevent oxidation and preserve flavour. It is also used as a bleaching agent in the production and/or processing of paper, wool, cotton etc.

Synonyms
E222, SBS, Sodium Hydrogen Sulfite, Sodium Pyrosulfite, Sodium Bisulfite, Sodium Bisulfite Solution, Sodium Bisulphite
Chemical Formula
NAHSO3
CAS Number
7631-90-5

Characteristics

Molar Weight
104.055 g/mol
Density
1.310 – 1.370
Forms
Yellow, Liquid (clear), Pale

Uses and applications

Key applications

  • Dyes
  • Photographic supplies
  • Wastewater treatment
  • Water treatment
  • Cleaning products
  • Fuel additive
  • Pulp and paper
  • Reducing agent
  • Bleaching agent

General information about sodium bisulphite

Sodium bisulphite (NaHSO3), also known as sodium hydrogen sulphite, is a sodium salt of sulphurous acid. Due to its high reactivity, the substance does not occur naturally. It decomposes into sodium sulphate and sulphur dioxide when exposed to air or heat, which is why it is only stable in an aqueous solution.

Properties of sodium bisulphite

Sodium bisulphite is a colourless to yellowish aqueous solution and has corrosive, reducing and bleaching properties. It is produced by:
  • Reaction of sulphur dioxide (SO2) with sodium hydroxide (NaOH)
  • Alternatively, sodium hydrogen sulphite can be produced by reacting sodium carbonate with SO2.
  • Sodium bisulphite is commercially available in 37 to 50 per cent solutions.

Sodium bisulphite in the food industry

Sodium bisulphite is used as E 222 and serves as a preservative, antioxidant and bleaching agent in the food and nutrition industry. It protects food from microbial decomposition, colour loss and oxidation. Examples of applications are:
  • Prevention of discolouration in fruit and vegetables.
  • Stabilisation of fruit juices, wine and dried fruit.
  • Lightening of flour, sugar and dried foods.

Sodium bisulphite in the pharmaceutical industry

In pharmaceutical products, sodium bisulphite acts as a reducing agent, preservative and antioxidant. It stabilises sensitive active ingredients and extends the shelf life of pharmaceutical solutions. Typical areas of application include:
  • Stabilisation of active ingredients such as vitamin C and adrenaline.
  • Inhibition of microbial growth in eye drops, infusion and injection solutions.
  • Support of pharmaceutical syntheses (e.g. sulphonamides).
Reduction of oxidative degradation products to their active form.
A smiling young woman holding a bottle of nasal spray

Sodium bisulphite in the cosmetics industry

In cosmetics, sodium hydrogen sulphite serves as an antioxidant, reducing and preservative ingredient. It protects sensitive formulations, inhibits discolouration and stabilises dyes. A characteristic range of applications can be seen in the following uses:
  • Stabilisation of sensitive ingredients (e.g. vitamin C).
  • Prevention of discolouration in creams and lotions.
  • Stabilisation of dyes in hair colourants.
  • Component of perming and straightening products.
  • Use in skin lightening products.
  • Stabilisation of anti-ageing formulations.
  • Improvement of emulsion consistency in make-up.
  • Stabilisation of dyes and solvents in nail care products.
The Solid Contact Clarifier Tank type Sludge Recirculation proce

Sodium biulphite in water treatment

Sodium bisulphite is an important dechlorinating and reducing agent in water treatment. It protects systems from corrosion and neutralises aggressive oxidising agents. Examples of this are:
  • Neutralisation of residual chlorine in drinking water and process systems.
  • Reduction of dissolved oxygen to prevent corrosion.
  • Neutralisation of peroxides and permanganates.
  • Protection of membranes in reverse osmosis plants.
  • Reduction of heavy metals in wastewater treatment

Further applications of sodium bisulphite

Sodium hydrogen sulphite in paper and pulp production

In the paper industry, sodium hydrogen sulphite is used as a decolourizing, reducing and dechlorinating agent. It prevents yellowing and improves optical quality. The most important areas of application include:
  • Removal of coloured compounds from wood fibres.
  • Prevention of yellowing by stabilising the cellulose.
  • Binding of iron and heavy metal ions.
  • Removal of printing inks in recycling processes.
  • Improvement of the print quality of coated papers.
  • Dechlorination of process water.

Sodium bisulphite in the construction industry

Sodium hydrogen sulphite is used in the construction industry as a reducing and cleaning agent to eliminate defects in concrete, raw materials and surfaces. Applications include:
  • Reduction of unwanted oxides in cement and raw materials.
  • Prevention of colour defects in concrete.
  • Removal of rust and discolouration on concrete, stone and natural stone.
  • Pickling of metals prior to coating or welding.
  • Reduction of wood discolouration.
  • Use in plasterboard production for visual stability.

Sodium hydrogen sulphite in the energy industry

In the energy sector, sodium hydrogen sulphite plays a central role in emission control, fuel stabilisation and process chemistry. Common areas of application are:
  • Flue gas desulphurisation through reduction of SO2.
  • Use as a fuel additive to reduce emissions.
  • Antioxidant in biodiesel and ethanol.
  • Reduction of oxidised metal compounds in process chemistry.
  • Oxygen removal in pipeline and drilling systems.
  • Dechlorination in cooling and boiler feed water.

Sodium hydrogen sulphite in textile manufacturing

In the textile industry, sodium bisulphite is used as a reducing agent - both for dyeing and decolourization. Examples of possible applications are:
  • Reduction dyeing (e.g. indigo for jeans).
  • Decolourization and bleaching of textiles.
  • Removal of excess dyes.
  • Ensuring uniform dyeing.

Sodium bisulphite in the rubber and caoutchouc industry

In the rubber industry, sodium bisulphite acts as a processing aid, stabiliser and reducing agent in rubber processing. It is used in the following areas, among others:
  • Stabiliser and reducing agent in latex and rubber production
  • Prevention of premature hardening
  • Optimisation of the material properties of technical rubber products

Sodium bisulphite in photography

Sodium bisulphite is used in photography as a reducing agent in development and fixing. It reduces the silver halide used and serves as an aid to prevent oxidation and stabilise the image.

Summary

Sodium hydrogen sulphite (NaHSO3, E 222) is a highly effective reducing agent, antioxidant and preservative that is indispensable in numerous industries. Due to its high reactivity in solution form and its ability to control oxidation processes, it plays a central role in the food, pharmaceutical, cosmetics, water, energy, textile, paper and construction industries.