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SODIUM SULFATE (Tentative)

 

New specifications prepared at the 53rd JECFA (1999) and published in FNP 52 Add 7 (1999).

Information required on technological effect and actual uses in foods and levels of metallic impurities including lead.

SYNONYMS

Glauber's salt, INS No. 514i

DEFINITION

 

C.A.S. number

7757-82-6 (Anhydrous)
7727-73-3 (Decahydrate)

Chemical formula

Na2SO4 xH2O (x = 0 or 10)

Formula weight

142.04 (Anhydrous)
322.19 (Decahydrate)

Assay

Not less than 99.0 % on the dried basis

DESCRIPTION

Colourless crystals or fine, white crystalline powder. The decahydrate is efflorescent.

FUNCTIONAL USES

Information required

CHARACTERISTICS

 

IDENTIFICATION

 

Solubility (FNP 5)

Freely soluble in water; practically insoluble in ethanol

Test for sodium (FNP 5)

Passes test

Test for sulfate (FNP 5)

Passes test

PURITY

 

Loss on drying (FNP 5)

Anhydrous: Not more than 1% (105, 4 h)
Decahydrate: Between 51.0% and 57.0%

Selenium (FNP 5)

Not more than 30 mg/kg
Test 0.2 g of the sample as directed in the Limit Test (Method II)

Lead (FNP5)

Not more than 2 mg/kg
Determine by atomic absorption spectroscopy (FNP 5)

Metallic impurities

Information required

METHOD OF ASSAY

Weigh accurately about 0.5 g of the dried sample, dissolve in 200 ml of water, add 1 ml of hydrochloric acid and heat to boiling. Gradually add, in small portions and while stirring constantly, an excess of hot barium chloride TS (about 10 ml), and heat the mixture on a steam bath for 1 h. Collect the precipitate on a filter, wash until free from chloride, dry, ignite and weigh. The weight of the barium sulfate so obtained, multiplied by 0.6086 corresponds to the equivalent amount of Na2SO4.

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