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EC number: 231-824-0 | CAS number: 7757-87-1
Hydrolysis
Administrative data
Link to relevant study record(s)
Description of key information
Key value for chemical safety assessment
Additional information
Trimagnesium bis(orthophosphate) (CAS 7757-87-1) is well soluble in water and dissociates to magnesium cations and phosphate species. A determination of the hydrolysis of the magnesium and the phosphate as function of pH according to OECD guideline 111 was not conducted since both ions have no potential mechanism for further hydrolysis or hydrolytic degradation.
The inorganic phosphates are normally found in different forms. In dilute aqueous solution, phosphate exists in four forms (see attachment). 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.
In a study evaluating the abiotic degradation of the anions of specified phosphates, pyrophosphates and triphosphates the hydrolytic half-live has been addressed by read across from a single example for each chemical class, where applicable. The ionic substances were assumed to undergo dissociation in aqueous solution and the resulting cation to have negligible influence on the hydrolysis rate of the anion within the buffer solutions used as instructed by Method 111 of the OECD Guidelines (Harlan, 2011).
The available data demonstrate that triphosphates and tripolyphosphates are hydrolytically stable under environmental conditions with a half-life > 1 year.
Chemical Class |
Substance Used for Experimental Determination |
Anticipated Half-Life at 25°C
|
|
Phosphates Orthophosphates |
Not applicable, no possible mechanism for hydrolysis |
pH4 > 1 year pH 7 > 1 year pH 9 > 1 year |
|
Pyrophosphates Diphosphates |
Tetrapotassium Pyrophosphate CAS 7320-34-5 |
pH4 > 1 year pH 7 > 1 year |
|
Triphosphates Tripolyphosphates |
Pentapotassium Triphosphate CAS 13845-36-8 |
pH 9 |
> 1 year |
pH4 pH 7 |
14.5 days > 1 year |
||
pH 9 |
> 1 year |
||
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