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Physical & Chemical properties

Dissociation constant

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Administrative data

Endpoint:
dissociation constant
Type of information:
not specified
Adequacy of study:
supporting study
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
other: basic knowledge of aluminium sulphate

Data source

Materials and methods

Results and discussion

Any other information on results incl. tables

Based on the basic knowledge of aluminium sulphate, the form of the inorganic substance in water varies from mononuclear to polynuclear hydroxo complex depending on the pH of solution:

Al3+→ [Al(OH) ]2+ → [Al(OH)2]+ → Al(OH)3(↓) → [Al(OH)4]- → [Al2O(OH)6]2-

pH < 4                                                                           → pH > 10

Due to physical-chemical properties (see section 4.8 water solubility), the substance dissolving in water results a strong acidic solution. Using the flask method , the water solubility of 202030/A at 20°C was ≥ 1000 g/l. The pH of the aqueous sample was 2.4. As a consequence in this aqueous solution, the Aluminium compound exists mainly as Aluminium ion and complexes of aluminium species [e. g. Al(OH)4-, the predominate species at higher pH], which are not expected to dissociate under naturally relevant pH (4-9) conditions.

In addition, in aqueous solution Al3+ does not occur as the free ion but is surrounded by six molecules of water to form (Al(H2O)6)3+. As pH increases, protons are removed from the co-ordinated waters to give various hydrolysis products. Progressive hydrolysis leads to the formation of aluminium hydroxide. (IUCLID ref 19); Concentrated commercial products are stable over months and years. When applied AS hydrolyses within minutes to Al(OH)3; Scientifically not necessary. Statement describing speciation to Al(OH)3. In aqueous solution Al3+ does not occur as the free ion but is surrounded by six molecules of water to form (Al(H2O)6)3+. As the pH increases, protons are removed from the co-ordinated waters to give various hydrolysis products. Progressive hydrolysis leads to the formation of aluminium hydroxide based on the study of hydrolysis of aluminium salts (see section 5.1.2 Hydrolysis), the hydrolysis of AlCl3with increased OH/Al was demonstrated as a process of polymeric aluminium species formation and decomposition.

Applicant's summary and conclusion

Conclusions:
The study of dissociation constant does not need to be conducted.