Sodium Metabisulfite BP


Sodium metabisulfite or sodium pyrosulfite is an inorganic compound of chemical formula Na2S2O5. The substance is sometimes referred to as disodium metabisulfite.  Sodium metabisulfite appears as a white crystalline or powder solid with a slight sulfur odor.



It is used as a disinfectant, antioxidant, and preservative agent. It can be used to preserve color of some fruits, such as bananas. It is commonly used in homebrewing and winemaking to sanitize equipment.



Molecular Formula:  Na2S2O5

Molecular Weight: 190.1 g/mol

CAS No.: 7681-57-4

Other name: Sodium Pyrosulphite



Test Specification
Characters It occurs as a white or almost white, crystalline powder or colorless crystals






(a)It complies with the test for pH-3.5 to 5.0

(b)Specified test. The solution is colorless and gives reaction of sulfates

(c) It gives positive reaction of sodium

Solubility Freely soluble in water, slightly soluble in ethanol (96%)
Appearance of Solution The solution  is clear and colorless
pH Between 3.5 to 5.0
Thiosulfates Specified Test. The solution remains clear for not less than 15 min
Arsenic Not more than 5 ppm
Iron Not more than 20 ppm
Heavy metals Not more than 20 ppm
Assay Not less than 95.0% and not more than the equivalent of 100.5% of Na2S2O5


Shelf life, Storage and Packing

It should be stored in a segregated area in a cool and ventilated place away from combustible materials. Keep in a tightly closed container, sealed until ready for use. It is packed in 25kg or 50kg HDPE bags or drums as required.


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We observe WHO Good manufacturing practice and Good laboratory practice.

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