Potassium alum, primarily composed of potassium aluminum sulfate dodecahydrate, possesses notable antimicrobial and astringent characteristics and is heavily integrated into Traditional Chinese Medicine. Within TCM theory, it is recognized for its capacity to detoxify, eradicate parasites, resolve dampness, relieve itching, stop bleeding, arrest diarrhea, clear heat, and dispel phlegm. Contemporary medical research validates its antibacterial and anti-trichomonal efficacy. Modern clinical practices in TCM utilize alum in managing hyperlipidemia, duodenal ulceration, and hemoptysis secondary to pulmonary tuberculosis.
Beyond medicinal uses, it serves as an essential raw material for manufacturing aluminum compounds, baking powders, coatings, tanning chemicals, clarifying agents, dye mordants, paper sizing agents, and waterproofing formulations. However, when ingested through food additives, accumulated aluminum compounds are poorly excreted and tend to deposit permanently in human tissues. Because aluminum is not an essential trace nutrient, excessive dietary intake disrupts the systemic absorption of key minerals such as iron and calcium, ultimately increasing the risk of anemia and osteoporosis.
| English name | Aluminium potassium sulfate dodecahydrate |
| English synonyms | POTASSIUM ALUMINIUM SULFATE 12-WATER;POTASSIUM ALUMINIUM SULFATE DODECAHYDRATE:POTAS SIUM ALUM:POTASSIUM ALUMINUM SULFATE DODECAHYDRATE:POTASSIUM ALUM SULFATE, DODECAHY DRATE;POTASSIUM ALUM DODECAHYDRATE;POTASSIUM AMMONIUM SULFATE;aluminumpotassiumdisulf atedodecahydrate |
| CAS number | 7784-24-9 |
| Molecular formula | AIH8KO5S |
| Molecular weight | 186.2 |
| EINECS number | 616-521-7 |
| Melting point | 92°C (lit.) |
| Boiling point | 200°C |
| Density | 1.757 g/mL at 25°C (lit.) |
| Bulk density | 900 kg/m³ |
| Storage conditions | Store at +5°C to +30°C |
| Solubility | H2O: 0.5M, clear, colorless |
| Form | Solid |
| Specific gravity | 1.757 |
| Color | White |
| Odor | Odorless |
| pH | 3.0-3.5 (25°C, 50 mg/mL in H2O) |
| Water solubility | 140 g/L (20°C) |
| Merck | 14,360 |
| Stability | Stable. Incompatible with steel, aluminum, copper, zinc, alkalis, and strong oxidizers. |
| LogP | -1.031 (est.) |
Alum's primary applications span a broad spectrum of industrial, technical, and medical uses:
Water Purification & Chemical Processing: Operates as an effective coagulant and sedimentation aid for clarifying turbid water, while serving as a pharmaceutical preservative, topical astringent, and local hemostatic agent.
Papermaking & Textile Manufacturing: Functions as an essential rosin sizing agent in paper production, along with acting as a key dye mordant, resist agent in anti-discharge printing, and dye retarder.
Photographic Processing & Industrial Additives: Serves as a film hardening agent in fixer solutions and photographic paper processing, while additionally finding use as a blowing agent in foam rubber manufacturing and as a food additive.
