K2CO3
DEFINITION
Content:
99.0 per cent to 101.0 per cent (dried substance).
CHARACTERS
Appearance:
White or almost white granular powder, hygroscopic.
Solubility: Freely soluble in water, practically insoluble in ethanol (96 per cent).
IDENTIFICATION
A. Dissolve 1 g in 10 ml of water. The solution is strongly alkaline.
B. 2 ml of the solution prepared for identification test A gives the reaction of carbonates and bicarbonates.
C. 1 ml of the solution prepared for identification test A gives reaction of potassium.
TESTS
Solution S:
Dissolve 10.0 g in 25 ml of distilled water. Slowly add 14 ml of hydrochloric acid. When the effervescence has ceased, boil for a few minutes. Allow to cool and dilute to 50 ml with distilled water.
Appearance of solution:
Solution S is not more opalescent than reference suspension and not more intensely coloured than reference solution.
Chlorides :
Maximum 100 ppm.
Sulphates :
Maximum 100 ppm.
Calcium: Maximum 100 ppm.
Iron: Maximum 10 ppm.
Heavy metals: Maximum 20 ppm.
Loss on drying: Maximum 5.0 per cent, determined on 0.300 g by drying in an oven at 120-125°C for 5 h.
ASSAY
Dissolve 0.500 g in 50 ml of carbon dioxide-free water. Carry out a potentiometric titration, using 1 M hydrochloric acid . Read the volume added at the 2nd point of inflexion.
1 ml of 1 M hydrochloric acid is equivalent to 69.1 mg of K2CO3.
K2CO3 (anhydrous) 138.21
Carbonic acid, dipotassium salt.
Dipotassium carbonate [584-08-7].
Sesquihydrate 165.23
Potassium Carbonate contains not less than 99.5 percent and not more than 100.5 percent of K2CO3, calculated on the dried basis.
Identification— It responds to the tests for Potassium and for Carbonate.
Loss on drying— Dry it at 180 for 4 hours: it loses not more than 0.5% of its weight.
Insoluble substances— Dissolve 1 g in 20 mL of water: the solution is complete, clear, and colorless.
Heavy metals— Dissolve 4.0 g in 10 mL of water, add 15 mL of 3 N hydrochloric acid, and heat to boiling. Add 1 drop of PhPh TS, and neutralize with 1 N sodium hydroxide until the solution is faintly pink in color. Cool, and dilute with water to 25 mL: the limit is 0.0005%.
Assay— Transfer the dried potassium carbonate obtained in the test for Loss on drying to a flask with the aid of 150 mL of water, add 4 drops of methyl orange TS, and titrate with 1 N hydrochloric acid VS. Each mL of 1 N hydrochloric acid is equivalent to 69.11 mg of K2CO3.
K2CO3 Formula wt, anhydrous 138.21
K2CO3·1½H2O Formula wt, hydrated 165.23
INS: 501(i) CAS: [584-08-7]
DESCRIPTION
Potassium Carbonate is anhydrous or contains 1.5 molecules of water of crystallization. The anhydrous form occurs as a white, granular powder, and the hydrated form as small, white, translucent crystals or granules. It is very deliquescent, and its solutions are alkaline. One gram dissolves in 1 mL of water at 25° and in about 0.7 mL of boiling water. It is insoluble in alcohol.
Function: pH control.
REQUIREMENTS
Identification: A 1:10 aqueous solution gives positive tests for Potassium and for Carbonate.
Assay: Not less than 99.0% and not more than 100.5% of K2CO3 after drying.
Insoluble Substances: Passes test.
Lead: Not more than 2 mg/kg.
Loss on Drying Anhydrous: Not more than 1%; Hydrated: Between 10.0% and 16.5%.
Potassium Carbonate, Anhydrous
K2CO3
Formula Wt 138.21
CAS Number 584-08-7
REQUIREMENTS
Assay: 99.0% K2CO3 min
MAXIMUM ALLOWABLE
Insoluble matter:
0.01%
Chloride (as Cl):
0.003%
Nitrogen compounds (as N):
0.001%
Phosphate (PO4):
0.001%
Silica (SiO2):
0.005%
Sulfur compounds (as SO4):
0.004%
Ammonium hydroxide precipitate 0.01%
Heavy metals (as Pb):
5 ppm
Iron (Fe):
5 ppm
Calcium:
0.005%
Magnesium:
0.002%
Sodium (Na):
0.02%
Potassium Carbonate Sesquihydrate
K2CO3 . 1.5H2O
Formula Wt 165.23
CAS Number 6381-79-9
REQUIREMENTS
Assay: 98.5-101.0% K2CO3 . 1.5H2O
Loss on heating at 285C: 14.0-16.5%
MAXIMUM ALLOWABLE
Insoluble matter: 0.01%
Chloride (as Cl): 0.003%
Nitrogen compounds (as N): 0.001%
Phosphate (PO4): 0.001%
Silica (SiO2): 0.005%
Sulfur compounds (as SO4): 0.004%
Ammonium hydroxide precipitate: 0.01%
Heavy metals (as Pb): 5 ppm
Iron (Fe): 5 ppm
Calcium (Ca): 0.005%
Magnesium (Mg): 0.002%
Sodium (Na): 0.02%
