ALUMINUM POTASSIUM SULFATE
PRODUCT IDENTIFICATION
CAS NO. 7784-24-9 (Decahydrate) 10043-67-1 (Anhydrous)

ALUMINUM POTASSIUM SULFATE
EINECS NO. 233-141-3
FORMULA AlK(SO4)2·12H2O
MOL WT. 474.37
H.S.CODE
TOXICITY
SYNONYMS Kalinite; Potash alum; Potassium alum dodecahydrate;
Alum; white alum; Aluminiumkaliumbis(sulfat) (German); Bis(sulfato) de aluminio y potasio (Spanish); Bis(sulfate) d’aluminium et de potassium (French); Sulfuric acid, aluminium potassium salt (2:1:1);
SMILES aluminium hydroxide with potassium sulfate in sulfuric acid
CLASSIFICATION
PHYSICAL AND CHEMICAL PROPERTIES
PHYSICAL STATE white crystals or powder
MELTING POINT 92 – 93 C
BOILING POINT 200 C (Decomposes)
SPECIFIC GRAVITY 1.757
SOLUBILITY IN WATER very soluble
pH 3 – 3.5 (10% solution)
VAPOR DENSITY 16.4
AUTOIGNITION
NFPA RATINGS Health: 1 Flammability: 0 Reactivity: 0
REFRACTIVE INDEX
FLASH POINT Not combustible
STABILITY Stable under ordinary conditions
GENERAL DESCRIPTION & APPLICATIONS
The term of alum refers to various isomorphous solid sulfates composed of trivalent metals and univalent metals, especially aluminum potassium sulfate, AlK(SO4)2·12H2O, a white, crystalline compound. Alums have the general formula M2SO4·MIII2(SO4)3·24H2O, where M is one of alkali metals (potassium, sodium, rubidium, caesium, silver. thallium or ammonium), and MIII denotes one of the trivalent cation (e.g., aluminum, chromium, iron, manganese, cobalt, or titanium). In aqueous solution, alums show all the chemical properties that their components show separately. These salts are used in water purification, leather tanning, coagulation agent for rubber latex, setting dyes (mordant), fireproofing textiles, modifying concrete, baking powder, preparation of lakes, clarifying of turbid liquids and as astringents.

  • Potassium aluminum sulfate (KAl(SO4)2·12H2O, CAS RN: 7784-24-9 (Dodecahydrate), 10043-67-1 (Anhydrous))
  • Sodium aluminum sulfate (NaAl(SO4)2·12H2O, CAS RN: 10102-71-3)
  • Ammonium aluminum sulfate (NH4Al(SO4)2·12H2O, CAS RN: 7784-25-0 (Anhydrous), 7784-26-1 (Dodecahydrate))
  • Chromium potassium sulfate (KCr(SO4)2·12H2O, CAS RN: 10141-00-1 (Anhydrous), 7788-99-0 (Dodecahydrate))
  • Aluminum fluorosulfate (FAl(SO4)2·12H2O, CAS RN: 73680-58-7)

Flocculants are used in water treatment. The addition of flocculants to raw water causes colloids and other suspended particles to stick together and form heavier particles (floc) which will be removed by the sedimentation or filterability. This flocculation (or called coagulation) process is to aid the removal of contaminants like fine solid pollutants or microscopic molecules which are difficult or impossible to be removed by filtration alone. Generally flocculants are multivalent cations such as aluminium, iron, calcium or magnesium. Many of the suspended water particles have a negative electrical charge which repels each other. Positively charged flocculants attract and stick to many of the suspended water particles. Many of flocculant s cations, under appropriate pH and other conditions, react with water to form insoluble hydroxides which join together to form larger settleable particles or physically traps small particles into the larger floc. There are organic flocculants also. The most common and powerful organic flocculant is polyacrylamide which have the long-chain to trap small particles into the larger floc. One of the common coagulants is aluminum sulfate which ,under neutral or slightly-alkaline conditions, reacts with water to form gelatinous precipitate of aluminum hydroxide. Polyaluminum chloride (PAC) of the general formula AlnCl(3n-m)(OH)m is useful as this compound have a wide range of pH value according to the subscripts n and m. The actual pH correlates to the formula m/(3n). It provides a choice forthe exact pH value applications. The most common PAC for water purification is Al12Cl12(OH)24. The form of Al2Cl(OH)5 is used as adeodorant and an antiperspirant. Other modified PAC compouinds include polyaluminum hydroxidechloride silicate (PACS) and polyaluminum hydroxidechloride silicate sulfate (PASS). Members of flocculants include:

  • Alum
  • Aluminum sulfate
  • Calcium oxide
  • Iron chloride
  • Iron sulfate
  • Polyacrylamide
  • Polyaluminum chloride
  • Polyaluminum hydroxidechloride silicate sulfate
  • Polyaluminum hydroxidechloride silicate
  • Sodium aluminate
  • Sodium silicate

PAC is also used in reducing the need of pH adjustment and is often employed in the place where the pH of the receiving stream is higher than 7.5. PAC is also used in the pulp (or paper) industry as a size bonding agent, drainage work aid and surface trash scavenger.