where can i buy sodium metabisulfite locally in kolkata india

Sodium metabisulfite or sodium pyrosulfite  is an inorganic compound of chemical formula Na2S2O5. The substance is sometimes referred to as disodium metabisulfite. It is used as a disinfectant, antioxidant, and preservative agent.

Uses

Food additive

It is used as a preservative and antioxidant in food and is also known as E223.

It may cause allergic reactions in those who are sensitive to sulfites, including respiratory reactions in asthmatics, anaphylaxis, and other allergic reactions in sensitive individuals.

Sodium metabisulfite and potassium metabisulfite are the primary ingredients in Campden tablets, used for wine and beer making.

The acceptable daily intake is up to 0.7 milligrams per kilogram of body weight. Sodium metabisulfite oxidizes in the liver to sulfate which is excreted in the urine.

Sanitization and cleaning agent

It is commonly used in homebrewing and winemaking to sanitize equipment. It is used as a cleaning agent for potable water reverse osmosis membranes in desalination systems. It is also used to remove chloramine from drinking water after treatment.

Other uses

Added to local anaesthetic (lidocaine etc.) solutions to prevent oxidation of vasoconstrictor adrenaline and thus improve the shelf life of the solution

It is used in photography.

Concentrated sodium metabisulfite can be used to remove tree stumps. Some brands contain 98% sodium metabisulfite, and cause degradation of lignin in the stumps, facilitating removal.

It is also used as an excipient in some tablets, such as paracetamol. Approximately 0.5 mg is used in epinephrine autoinjectors such as the EpiPen.

A very important health related aspect of this substance is that it can be added to a blood smear in a test for sickle cell anaemia (and other similar forms of haemoglobin mutation). 

The substances causes defunct cells to sickle (through a complex polymerisation) hence confirming disease.

It is used as the source of SO2 in wine. An important anti-oxidant and bactericide

It is also used to precipitate gold from auric acid (gold dissolved in aqua regia).

It is used in waste treatment to chemically reduce hexavalent chromium to trivalent chromium which can then be precipitated and removed from an aqueous waste stream.

It is used as a bleaching agent in the production of Coconut cream.

It is used as a reducing agent to break sulfide bonds in shrunken items of clothing made of natural fibers, thus allowing the garment to go back to its original shape after washing.

It is used as an SO2 source (mixed with air or oxygen) for the destruction of cyanide in commercial gold cyanidation processes.

It is used in the oil and gas industry as a corrosion inhibitor/oxygen scavenger.

It is used in the water treatment industry to quench chlorine residual.

It is used in tint etching iron-based metal samples for microstructural analysis