Name: Potassium Alum
CAS No: Aluminum potassium sulfate anhydrous [10043-67-1], Aluminum potassium sulfate dodecahydrate [7784-24-9]
BP: Alum JP: Aluminum Potassium Sulfate Hydrate PhEur: Alum USP: Potassium Alum
Alumen; alum flour; alum meal; alum potassium; aluminum potassium alum; aluminum potassium disulfate; aluminum potassium sulfate; dialuminum dipotassium sulfate; kalinite; potash alum; potassium aluminum sulfate (1 : 1 : 2); potassium aluminum sulfate-12-hydrate; rock alum; sulfuric acid aluminum potassium salt (2 : 1 : 1) dodecahydrate
Aluminum potassium sulfate anhydrous [10043-67-1], Aluminum potassium sulfate dodecahydrate [7784-24-9]
AlK(SO4)2 258.21 (for anhydrous) AlK(SO4)212H2O 474.39 (for dodecahydrate)
See Section 4.
Potassium alum precipitates proteins and is a powerful astringent. The ability to precipitate proteins is utilized in the manufacture of vaccines, where purified proteins are coprecipitated with and adsorbed onto potassium alum.(1,2) Potassium alum is often included in preparations used as mouthwashes or gargles and in dermatological preparations, and it may be used as a topical hemostatic, either as a solid or as a solution. Intravesical instillation of potassium alum, typically as a 1% solution, has been used for hemorrhagic cystitis.
The PhEur 6.0 describes potassium alum as a granular powder, or colorless, transparent, crystalline masses. The JP XV describes it as colorless or white crystals or powder. Potassium alum is odorless and has a slightly sweet, strongly astringent taste.
See Table I.
Density (bulk) 1 g/cm3(3) Density (true) 1.725 g/cm3 Melting point 92.58C Acidity/alkalinity pH = 3.0–3.5 (10% w/v aqueous solution at 208C) Solubility Freely soluble in water, very soluble in boiling water; soluble in glycerol; practically insoluble in ethanol (96%). Vapor density (relative) 16.4 (air = 1)(4)
Store in a cool, dry place in tightly closed containers. Stable under normal temperatures and pressures. When kept for a long time at 60–658C (or over sulfuric acid) potassium alum dodecahydrate loses water, which is reabsorbed on exposure to air. It becomes anhydrous at about 2008C.
Potassium alum is incompatible with strong oxidizing agents, aluminum, copper, steel, and zinc. When it is dispensed in powders with phenol, salicylates, or tannic acid, gray or green colors may be developed owing to traces of iron in the alum.
Potassium alum is manufactured by treating bauxite with sulfuric acid and then potassium sulfate. Alternatively, aluminum sulfate is reacted with potassium sulfate.(5)
Potassium alum is often included in preparations used as mouthwashes or gargles and in dermatological preparations. Large doses of potassium alum act as an irritant and may be corrosive; gum necrosis and gastrointestinal hemorrhage have occurred. Acute encephalopathy has been reported(6,7) following bladder irrigation with alum solutions in the treatment of bladder hemorrhage. Anecdotal evidence suggests that this practice should be avoided for patients with renal insufficiency.(6)
Observe normal precautions appropriate to the circumstances and quantity of the material handled. It causes eye and skin irritation and may cause respiratory tract irritation. During a fire, irritating and highly toxic gases may be generated by thermal decomposition or combustion of potassium alum. Hazardous decomposition products include oxides of sulfur, aluminum oxide, and oxides of potassium. The American Conference of Governmental Industrial Hygienists (ACGIH) value for potassium alum is 2 mg/m3 TWA (as aluminum)
GRAS listed. Included in the FDA Inactive Ingredients Database (vaginal; suppository). Included in medicines licensed in the UK.
The JP XV has separate monographs for aluminum potassium sulfate and dried aluminum potassium sulfate. A specification for potassium alum is contained in the Food Chemicals Codex (FCC).(8) The EINECS number for potassium alum (anhydrous) is 233- 141-3. The PubChem Compound ID (CID) for potassium alum dodecahydrate is 62667.