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Sodium metabisulfite, also known as sodium pyrosulfite, is a chemical substance used in a variety of applications. As a reducing agent and antioxidant, it is widely used both in industry and in households. In this blog post, we want to take a closer look at the properties, applications, and safety aspects of sodium metabisulfite.

What is sodium metabisulfite?

Sodium metabisulfite (Na₂S₂O₅) is a white, crystalline powder that is soluble in water. It is produced by drying sodium bisulfite and belongs to the sulfite compounds. Due to its reducing properties, sodium metabisulfite is often used as an antioxidant and preservative.

Chemical Properties

Sodium metabisulfite is a strong reducing agent that easily absorbs oxygen and reacts to form sodium sulfite (Na₂SO₃). This process can be reversible, so sodium metabisulfite can also act as an oxygen absorber. Furthermore, it reacts with water to form sulfur dioxide (SO₂), which is important for many applications.

The chemical formula is:

Na₂S₂O₅ + H₂O ⇌ 2 NaHSO₃

In addition to its reducing properties, sodium metabisulfite also has some acidity and can thus lower the pH value in solutions.

Industrial applications of sodium metabisulfite

In industry, sodium metabisulfite has a wide range of uses. Some of the most important application areas are:

Gas desulfurization

One of the main applications of sodium metabisulfite is the desulfurization of industrial gases. By reacting with sulfur compounds such as hydrogen sulfide (H₂S), sodium metabisulfite can effectively remove them from exhaust gases, thereby reducing environmental pollution.

Chemical Industry

In the chemical industry, sodium metabisulfite serves as a reducing agent and antioxidant in the production and processing of various chemicals. It is used in the manufacture of dyes, plastics, rubber, and other industrial products.

Food industry

In the food industry, sodium metabisulfite is used as a preservative and antioxidant. It prevents browning of fruits and vegetables, protects wines and fruit juices from oxidation, and extends the shelf life of foods.

Water treatment

In water treatment, sodium metabisulfite is used to remove chlorine and other oxidizing agents from drinking and wastewater. This enables safe disinfection and treatment of the water.

Pharmaceutical industry

Sodium metabisulfite is also used in the pharmaceutical industry. It is used as an excipient in medicines to increase their shelf life and prevent oxidation processes.

Household applications

Besides the diverse industrial applications, sodium metabisulfite also has some useful household uses:

Food preservation

Similar to the food industry, sodium metabisulfite can also be used in households to preserve foods such as fruits, vegetables, wine, or fruit juices. It prevents spoilage and extends shelf life.

Disinfection and cleaning

Sodium metabisulfite is used as a disinfectant for surfaces, textiles, and dishes. Due to its antioxidative properties, it is also suitable for cleaning and mold removal.

Decolorization

Due to its reducing effect, sodium metabisulfite can be used for decolorizing textiles, paper, or wood. It effectively removes stains and discolorations.

Swimming pool maintenance

In swimming pool maintenance, sodium metabisulfite is used to bind chlorine and reduce the chlorine content in the water. This reduces the burden on bathers.

Safety aspects and handling

Although sodium metabisulfite is considered safe in many applications, some precautions must be observed when handling it:

• Sodium metabisulfite can cause irritation upon contact with eyes, skin, or mucous membranes. Protective equipment such as gloves and safety goggles is therefore recommended.
• In combination with acids or heat, sodium metabisulfite can release sulfur dioxide, which may cause respiratory irritation. Good ventilation is therefore important.
• For people with sulfite allergy or asthma, sodium metabisulfite can cause health problems. In such cases, alternative preservatives should be used.
• When storing and disposing of sodium metabisulfite, applicable regulations must be observed to avoid environmental damage.

Overall, sodium metabisulfite, when handled properly, is a useful and safe chemical substance with a wide range of applications in industry and household.