Potassium Alum

Synonyms: Potassium alum, Potash alum, Aluminum potassium sulphate dodecahydrate, Potassium aluminum sulphate dodecahydrate,

CAS Number: 7784-24-9,

Molecular Weight: 474.39,

Chemical Formula: AlK(SO4)2.12H2O,

EINECS EC Number: 233-141-3,

FEMA: ...

Alum BP

Potash Alum BP
Aluminium Potassium Sulphate BP

Content: 99.0 per cent to 100.5 per cent of AlK(SO4)2,12H2O.

Appearance: Granular powder or colourless, transparent, crystalline masses.
Solubility: Freely soluble in water, very soluble in boiling water, soluble in glycerol, practically insoluble in ethanol (96 per cent).

A. Solution S (see Tests) gives the reactions of sulphates.
B. Solution S gives the reaction of aluminium.
C. Shake 10 ml of solution S with 0.5 g of sodium bicarbonate R and filter. The filtrate gives reaction (a) of potassium.

Solution S : Dissolve 2.5 g in water R and dilute to 50 ml with the same solvent.
Appearance of solution: Solution S is clear and colourless.
pH: 3.0 to 3.5.
Ammonium: Maximum 0.2 per cent.
Iron: Maximum 100 ppm.
Heavy metals: Maximum 20 ppm.

Potassium Alum USP

Aluminum Potassium Sulfate USP
AlK(SO4)2·12H2O 474.39
Sulfuric acid, aluminum potassium salt (2:1:1), dodecahydrate.
Aluminum potassium sulfate (1:1:2) dodecahydrate [7784-24-9].
Anhydrous 258.21 [10043-67-1].

Potassium Alum contains not less than 99.0 percent and not more than 100.5 percent of AlK(SO4)2, calculated on the dried basis.

A: Add 1 N sodium hydroxide drop wise to a solution of it (1 in 20): a precipitate is formed that dissolves in an excess of the reagent. Ammonia is not evolved (distinction from Ammonium Alum).
B: Hold it in a non-luminous flame: a violet color is imparted to the flame.
C: Add 10 mL of sodium bitartrate TS to 5 mL of a saturated solution of it: a white, crystalline precipitate is formed within 30 minutes.
D: A solution (1 in 20) responds to the tests for Aluminum and for Sulfate.
Loss on drying: Transfer 2.0 g, in a tarred porcelain crucible, to a muffle furnace at 200. Increase the temperature to 400 and dry at 400 to constant weight. Cool in a desiccator, and weigh: it loses between 43.0% and 46.0% of its weight.
Heavy metals: the limit is 0.002%.
Iron: Add 5 drops of potassium ferro-cyanide TS to 20 mL of a solution (1 in 150): no blue color is produced immediately.

Aluminum Potassium Sulfate FCC Food Grade

Potassium Alum FCC
AlK(SO4)2·12H2O Formula wt 474.38
INS: 522 CAS: [7784-24-9]

Aluminum Potassium Sulfate occurs as large, transparent crystals or crystalline fragments, or as a white crystalline powder. One gram dissolves in 7.5 mL of water at 25° and in about 0.3 mL of boiling water. Its solutions are acid to litmus. It is insoluble in alcohol, but is freely soluble in glycerin.

Identification: A 1:20 aqueous solution gives positive tests for Aluminum, for Potassium, and for Sulfate.
Assay: Not less than 99.5% and not more than 100.5% of AlK(SO4)2·12H2O.
Ammonium Salts: Passes test.
Fluoride: Not more than 0.003%.
Lead: Not more than 3 mg/kg.
Selenium: Not more than 0.003%.

Aluminum Potassium Sulfate Dodecahydrate Analytical Reagent

Potash Alum
AlK(SO4)2 . 12H2O
Formula Wt 474.39
CAS Number 7784-24-9

Assay: 98.0-102.0% AlK(SO4)2 .12H2O

Insoluble matter: 0.005%
Chloride (Cl): 5 ppm
Ammonium (NH4): 0.005%
Heavy metals (as Pb): 0.001%
Iron (Fe): 0.001%
Sodium (Na): 0.02%