Registration Dossier
Registration Dossier
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EC number: 236-715-1 | CAS number: 13466-20-1
Hydrolysis
Administrative data
Link to relevant study record(s)
Description of key information
Key value for chemical safety assessment
Additional information
When released to water barium bis(dihydrogenorthophosphate) dissociates to barium cations and phosphate species.
A determination of the hydrolysis of the barium cation and the phosphate anions according to OECD guideline 111 was not conducted since Barium bis(dihydrogen orthophosphate) dissociates. The hydrolysis of barium and phosphate species is well studied. Furthermore, both ions have no potential mechanism for further hydrolysis or degradation.
Ba exists in aquatic environment basically in form of Ba+2 independent upon pH, Eh (redox) (Nato, 2005).
Phosphoric acid is a weak acid that does not fully dissociate in water. Salts containing the anion H2PO4¯ are weakly acidic. In dilute aqueous solution hydrolysis , equilibria establishs among the following four species (Figure 1): In strongly-basic conditions, the phosphate ion (PO43−) predominates, whereas in weakly-basic conditions, the hydrogen phosphate ion (HPO42−) is prevalent. In weakly-acid conditions, the dihydrogen phosphate ion (H2PO4−) is most common. In strongly-acid conditions, aqueous phosphoric acid (H3PO4) is the main form. Various phosphate ions maintain a dissociation equilibrium state and are present as dominant phosphorus species in water under the normal environmental conditions.
Phosphates exist in aqueous solution in different formsdepending on pH conditions.
Monohydrogen and dihydrogen phosphates act as buffer over a pH range of 6 – 8 and have an important biological function in the aquatic environment.
As ions monohydrogen and dihydrogen phosphates are well soluble in water. However, they can be incorporated into either biological solids (e.g. microorganisms) or chemical precipitates and removed from water, such as formation of insoluble compounds in presence of aluminium and other transition cations.
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