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Prepared at the 29th JECFA (1985), published in FNP 34 (1986) and in FNP 52 (1992) |
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SYNONYMS |
INS No. 515 |
DEFINITION | |
Chemical names |
Potassium sulfate |
C.A.S. number |
7778-80-5 |
Chemical formula |
K2O4S |
Structural formula |
K2SO4 |
Formula weight |
174.25 |
Assay |
Not less than 99.0% |
DESCRIPTION |
Colourless or white crystals or crystalline powder |
FUNCTIONAL USES |
Salt substitute |
CHARACTERISTICS | |
IDENTIFICATION | |
Solubility |
Freely soluble in water, insoluble in ethanol |
pH |
5.5 - 8.5 (1 in 20 soln) |
Test for potassium |
Passes test |
Test for sulfate |
Passes test |
PURITY | |
Arsenic |
Not more than 3 mg/kg (Method II) |
Heavy metals |
Not more than 10 mg/kg Test a solution of 3 g of the sample in 25 ml of water as directed in the Limit Test (Method I) |
Selenium |
Not more than 30 mg/kg Test 0.2 g of the sample as directed in the Limit Test (Method II) |
METHOD OF ASSAY |
Weigh accurately about 0.5 g of the 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 8 or 9 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 0.7466, indicates its equivalent of K2SO4. |