Potassium aluminium sulfate

Potassium aluminium sulfate (CAS 10043-67-1), commercially known as potassium alum and approved as E522, is an inorganic double salt used across food, water treatment, and industrial processing.

Where is Potassium aluminium sulfate used?

• Water treatment: flocculant that aggregates particles, clarifying drinking water and wastewater streams
• Food and beverage: firming agent and leavening component in baked goods, pickled products, and starch-based formulations
• Tanneries and leather processing: primary tanning and preserving agent
• Textile dyeing: mordant that bonds dyes to natural fibers, improving wash fastness and color consistency
• It functions as a coagulant, astringent, and pH buffer.
• Fire retardants: historically applied to timber as alum solutions.
• Construction: accelerates the hardening of concrete and plaster.
• Medical sector: mainly used as an astringent or hemostatic antiseptic.
• Electroplating: acts as a buffer in zinc sulfate plating to stabilize bath pH.

Good to know: Its astringent action fixes hides without the environmental burden of chromium-based alternatives. Buyers typically specify grade and crystal size based on dissolution rate requirements.

Formulation notes

• Dissolves slowly in glycerol; insoluble in ethanol and acetone.
• Should not be stored with strong oxidizing agents and metals.

Typical specification

• Supplied in white fine crystal form.
• Solubility: 14.00 g/100 mL at 20 °C.
• Melting point: 92 °C.
• Maximum impurity content: 0.05%.

Regulatory status

• Not classified as a hazardous substance or mixture under EU Regulation (EC) No 1272/2008.
• German water hazard class: 3.
• Not subject to transport regulations.

Storage, packaging and handling

• Commonly store in a cool, dry area with the bag unopened.

Frequently asked questions about Potassium aluminium sulfate

At what temperatures does the dodecahydrate form lose its water of crystallization?

The dodecahydrate loses its first nine water molecules at 64.5°C (64 °C) and the remaining three at about 200°C (200 °C).

Can potassium aluminium sulfate serve as a precursor in the manufacture of other aluminium salts?

It is used as a raw material in the production of aluminium salts.

Technical content is compiled and updated by the SoleChem product team from public technical sources; the certificate of analysis (COA) governs product-specific specifications.