ANNEX I

E 522 ALUMINIUM POTASSIUM SULPHATE

Synonyms

Potassium alum, potash alum

Definition

Chemical name

Aluminium potassium sulphate dodecahydrate

Einecs

233-141-3

Chemical formula

AlK(SO4)2 · 12 H2O

Molecular weight

474,38

Assay

Content not less than 99,5 %

Description

Large, transparent crystals or white crystalline powder

Identification

A.

Positive tests for aluminium, for potassium and for sulphate

B.

pH of a 10 % solution between 3,0 and 4,0

C.

Solubility

Freely soluble in water, insoluble in ethanol

Purity

Ammonium salts

No odour of ammonia detectable after heating

Selenium

Not more than 30 mg/kg

Fluoride

Not more than 30 mg/kg

Arsenic

Not more than 3 mg/kg

Lead

Not more than 5 mg/kg

Mercury

Not more than 1 mg/kg