Sodium Metabisulphite B

Sodium Pyrosulphite
Na2S2O5

DEFINITION
Sodium metabisulphite also called sodium disulphite.
Content : 95.0 per cent to 100.5 per cent.

CHARACTERS
Appearance: White or almost white, crystalline powder or colourless crystals.
Solubility: Freely soluble in water, slightly soluble in ethanol (96 per cent).

IDENTIFICATION
A. pH 3.5 to 5.0 for solution S.
B. To 0.4 ml of iodinated potassium iodide solution R add 8 ml of distilled water R and 1 ml of solution S diluted 1 to 10 in distilled water R. The solution is colourless and gives reaction of sulphate.
C. Solution S gives reaction of sodium.

TESTS
Solution S: Dissolve 5.0 g in carbon dioxide-free water prepared from distilled water and dilute to 100 ml with the same solvent.
Appearance of solution : Solution S is clear and colourless.
pH: 3.5 to 5.0 for solution S.
Thiosulphate: To 5 ml of solution S add 5 ml of dilute hydrochloric acid R. The solution remains clear for at least 15 min.
Arsenic: Maximum 5 ppm.
Iron: Maximum 20 ppm, determined on solution S.
Heavy metals: Maximum 20 ppm.

Sodium Metabisulfite USP NF

Na2S2O5 -- 190.11
Disulfurous acid, disodium salt.
Disodium pyrosulfite [7681-57-4]

Sodium Metabisulfite contains an amount of Na2S2O5 equivalent to not less than 65.0 percent and not more than 67.4 percent of SO2.

Packaging and storage— Preserve in well-filled, tight containers, and avoid exposure to excessive heat.
Identification— A solution (1 in 20) responds to the tests for Sodium 191 and for Sulfite.
Limit of chloride— Dissolve 1.0 g in 10 mL of water, filter, if necessary, through a small chloride free filter, and add 6 mL of 30 percent hydrogen peroxide. Add 1 N sodium hydroxide until the solution is slightly alkaline to phenolphthalein, dilute with water to 100 mL, and mix. Dilute 2.0 mL of this solution with water to 20 mL, and add 1 mL of nitric acid and 1 mL of silver nitrate TS. Mix, allow to stand for 5 minutes protected from direct sunlight, and compare the turbidity, if any, with that produced from a 2-mL aliquot of a control (prepared by diluting 0.71 mL of 0.020 N hydrochloric acid to 100 mL) in an equal volume of total solution containing the quantities of reagents used in the test : any turbidity produced by the test specimen does not exceed that of the control preparation (0.05%).
Iron—: the limit is 0.002%.
Limit of thiosulfate— Mix 2.2 g with 10 mL of 1 N hydrochloric acid in a 50-mL beaker. Boil gently for 5 minutes, cool, and transfer to a small test tube. Any turbidity is not greater than that produced by 0.10 mL of 0.10 N sodium thiosulfate, similarly treated (0.05%).
Heavy metals—: the limit is 0.002%.

Sodium Metabisulfite FCC Food Grade
Sodium Pyrosulfite
Na2S2O5 Formula wt 190.11
INS: 223 CAS: [7681-57-4]

DESCRIPTION
Sodium Metabisulfite occurs as colorless crystals or as a white to yellow, crystalline powder. It is freely soluble in water and slightly soluble in alcohol. Its solutions are acid to litmus.
Function: Preservative; antioxidant.

REQUIREMENTS
Identification: A 1:10 aqueous solution gives positive tests for Sodium and for Sulfite.
Assay: Not less than 90.0% and not more than 100.5% of Na2S2O5.
Iron: Not more than 10 mg/kg.
Lead: Not more than 2 mg/kg.
Selenium: Not more than 5 mg/kg.

Sodium Metabisulfite Analytical Reagent

Disodium Disulfite
Na2S2O5
Formula Wt 190.11
CAS Number 7681-57-4