DEFINITION
Content:
48.0 per cent to 52.5 per cent of Na2SO3.
CHARACTERS
Appearance:
Colourless crystals.
Solubility:
Freely soluble in water, very slightly soluble in ethanol (96 per cent).
IDENTIFICATION
A. Solution S (see Tests) is slightly alkaline.
B. To 5 ml of solution S add 0.5 ml of 0.05 M iodine. The solution is colourless and gives reaction of sulphates.
C. Solution S gives reaction (a) of sodium (2.3.1).
D. It complies with the limits of the assay.
TESTS
Solution S:
Dissolve 10 g in water R and dilute to 100 ml with the same solvent.
Solution S1:
To 20.0 g add 25 ml of water R . Shake until mostly dissolved, and carefully and progressively, add 15 ml of hydrochloric acid R . Heat to boiling. Cool and dilute to 100.0 ml with water.
Appearance of solution: Solution S is clear and colourless.
Thiosulphates:
Maximum 0.05 per cent.
Iron:
Maximum 5 ppm, determined on solution S1.
Selenium:
Maximum 5 ppm.
Zinc:
Maximum 12.0 ppm.
Heavy metals:
Maximum 5 ppm.
Na2SO3 126.0 [7757-83-7]
Contains not less than 95.0 percent and not more than 100.5 percent of Na2SO3
Identification:
A: Dissolve 5 g of in 100 mL of water. [NOTE—Reserve portions of the solution so obtained for use in Identification test B and in the test for Color and clarity of solution.] Add a drop of phenolphthalein TS: a pink color is produced.
B: To 5 mL of the solution from Identification test A, add 0.5 mL of iodine TS: the solution is colorless, and it meets the requirements of the barium chloride test for Sulfate.
C: It meets the requirements of the pyroantimonate precipitate test for Sodium.
Color and clarity of solution: Examine the solution prepared for Identification test A: the solution is clear and colorless.
Heavy metals: 10 3g per g, the Test Preparation being prepared as follows. To 8.0 g of Sodium Sulfite add 25 mL of water. Shake until mostly dissolved, and slowly and carefully add 15 mL of hydrochloric acid. Heat to boiling. Cool, and dilute with water to 100.0 mL. Use a 25-mL portion.
Limit of iron: not more.
Limit of selenium: not more than 10 3g per g is found.
Limit of thiosulfates: not more than 25 µg per g is found.
Na2SO3 Formula wt 126.04
INS: 221 CAS: [7757-83-7]
DESCRIPTION
It occurs as a white or tan to slightly pink powder. It undergoes oxidation in air. Its solutions are alkaline to litmus and to phenolphthalein. One gram dissolves in about 4 mL of water. It is sparingly soluble in alcohol.
Function: Preservative; antioxidant; bleaching agent.
REQUIREMENTS
Identification: A 1:20 aqueous solution gives positive tests for Sodium and for Sulfite.
Assay: Not less than 95.0% of Na2SO3.
Lead: Not more than 2 mg/kg.
Selenium: Not more than 0.003%.
Na2SO3
Formula Wt 126.04
CAS Number 7757-83-7
REQUIREMENTS
Assay: minimum 98.0% Na2SO3
