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What are the properties of aluminum sulfate?


Aluminum sulfate (chemical formula Al2(SO4)3, formula quantity 342.15), white rhombohedral crystalline powder, density 1.69g/mL (25℃). In the paper industry as rosin gum, wax emulsion and another gum precipitant, water treatment as a flocculant, also can be used as a foam fire extinguisher internal retention agent, the manufacture of alum, aluminum white raw materials, petroleum decolorization, deodorant, raw materials for certain drugs, etc... It can also be used to manufacture artificial gemstones and high-grade ammonium alum.


The first major use of aluminum sulfate, which accounts for about 50% of the total production, is for paper making, and the second major use is as a flocculant in drinking water, industrial water, and industrial wastewater treatment, which accounts for about 40% of the total aluminum sulfate production. When aluminum sulfate is added to this type of water, it can be produced into a colloidal, aluminum hydroxide floc that can adsorb and precipitate out bacteria, colloids, and other suspended matter be used in drinking water treatment to control the color and taste of water.

Aluminum sulfate

【Basic Information】

English name

aluminium sulfate










Soluble in water, insoluble in ethanol, etc.

Appearance and properties

White crystal, sweet smell

Relative density (water=1)




【Physical and chemical properties】

The industrial product is off-white flake, granular or lumpy, with light green color due to low iron salt content, and yellow surface due to oxidation of low valent iron salt. Coarse product is gray-white fine crystal structure porous material.

It is extremely soluble in water. Aluminum sulfate cannot be dissolved in pure sulfuric acid (just coexist), and it is co-dissolved in water with sulfuric acid in sulfuric acid solution, so the solubility of aluminum sulfate in sulfuric acid is the solubility of aluminum sulfate in water.

There are anhydrous substance and octadecyl hydrate. The anhydrous substance is colorless rhombohedral crystal. It is soluble in water, and the aqueous solution is acidic, slightly soluble in ethanol. The solubility in water increases with the increase of temperature. Octadecahydrate (Al2-(SO4)3-18H2O) is a colorless monoclinic crystal. It is soluble in water and insoluble in ethanol. The aqueous solution is acidic due to hydrolysis.

【Chemical properties】

Not easy to weather and lose water of crystallization, relatively stable, will lose water when heated, will decompose into aluminum oxide and sulfur oxide at high temperature.

Heated to 770℃, it starts to decompose into aluminum oxide, sulfur trioxide, sulfur dioxide and water vapor. Soluble in water, acid and alkali, insoluble in ethanol. Aqueous solution is acidic. Hydrolysis produces aluminum hydroxide. Boiling of aqueous solution for a long time can produce basic aluminum sulfate. Non-toxic, the dust can irritate the eyes.

Hydrolysis products have alkali salt and aluminum hydroxide colloidal precipitate. Easily combined with salts of potassium, sodium and ammonium to form alum, such as potassium aluminum sulfate kAl(SO4)2-12H2O.

When heated hydrate, it swells violently and becomes spongy, and when heated to red heat, it decomposes into sulfur trioxide and aluminum oxide.


ADI not specified (FAO/WHO, 2001).

GRAS (FDA,§182.1125, 2000).

LD50: 980±90 mg/kg (oral in mice).


【Main use】

Used as an effective cross-linking agent for animal glue, and can improve the viscosity of animal glue. Also used as curing agent of urea-formaldehyde adhesive, 20% aqueous solution curing speed is faster.

In the paper industry, it is used as the precipitant of rosin gum, wax emulsion and other gum materials, as flocculant in water treatment, and as the internal retention agent of foam fire extinguisher, as the raw material of manufacturing alum and aluminum white, as the raw material of oil decolorization, deodorizer and some drugs. It can also be used to make artificial gemstones and high grade ammonium alum. Products with arsenic content not more than 5mg/kg can be used as water treatment flocculant.

1. Used as paper sizing agent in paper industry to enhance the water resistance and impermeability of paper.

2. Dissolved in water, it can make the fine particles and natural gum particles in water coalesce into large flocs, which can be removed from water, so it is used as coagulant for water supply and wastewater.

3. Used as turbid water purifying agent, also used as precipitating agent, color fixing agent, filling agent, etc. Used as raw material of anti-sweat cosmetics (astringent) in cosmetics.

4. In the fire-fighting industry, it is used as a foam extinguishing agent with baking soda and foaming agent.

5. Analytical reagent, mordant, tanning agent, oil decolorizer, wood preservative.

6. Stabilizer for albumin pasteurization (including liquid or frozen whole egg, egg white or egg yolk).

7. as raw materials for the manufacture of artificial stones and high grade ammonium alum, other aluminates.

8. In the fuel industry, in the production of chrome yellow and color precipitation dyes as a precipitating agent, and at the same time play a solid color and filler role.


Flammability hazard: The product is non-flammable and irritating.

Health hazard: It is irritating to eyes and mucous membranes. Accidental ingestion of large amounts of aluminum sulfate has an irritating effect on the mouth and stomach.

Toxicological data: Oral LC50 in mice: 6207mg/kg.

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