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Diss Factsheets
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EC number: 235-285-2 | CAS number: 12158-74-6
- Life Cycle description
- Uses advised against
- Endpoint summary
- Appearance / physical state / colour
- Melting point / freezing point
- Boiling point
- Density
- Particle size distribution (Granulometry)
- Vapour pressure
- Partition coefficient
- Water solubility
- Solubility in organic solvents / fat solubility
- Surface tension
- Flash point
- Auto flammability
- Flammability
- Explosiveness
- Oxidising properties
- Oxidation reduction potential
- Stability in organic solvents and identity of relevant degradation products
- Storage stability and reactivity towards container material
- Stability: thermal, sunlight, metals
- pH
- Dissociation constant
- Viscosity
- Additional physico-chemical information
- Additional physico-chemical properties of nanomaterials
- Nanomaterial agglomeration / aggregation
- Nanomaterial crystalline phase
- Nanomaterial crystallite and grain size
- Nanomaterial aspect ratio / shape
- Nanomaterial specific surface area
- Nanomaterial Zeta potential
- Nanomaterial surface chemistry
- Nanomaterial dustiness
- Nanomaterial porosity
- Nanomaterial pour density
- Nanomaterial photocatalytic activity
- Nanomaterial radical formation potential
- Nanomaterial catalytic activity
- Endpoint summary
- Stability
- Biodegradation
- Bioaccumulation
- Transport and distribution
- Environmental data
- Additional information on environmental fate and behaviour
- Ecotoxicological Summary
- Aquatic toxicity
- Endpoint summary
- Short-term toxicity to fish
- Long-term toxicity to fish
- Short-term toxicity to aquatic invertebrates
- Long-term toxicity to aquatic invertebrates
- Toxicity to aquatic algae and cyanobacteria
- Toxicity to aquatic plants other than algae
- Toxicity to microorganisms
- Endocrine disrupter testing in aquatic vertebrates – in vivo
- Toxicity to other aquatic organisms
- Sediment toxicity
- Terrestrial toxicity
- Biological effects monitoring
- Biotransformation and kinetics
- Additional ecotoxological information
- Toxicological Summary
- Toxicokinetics, metabolism and distribution
- Acute Toxicity
- Irritation / corrosion
- Sensitisation
- Repeated dose toxicity
- Genetic toxicity
- Carcinogenicity
- Toxicity to reproduction
- Specific investigations
- Exposure related observations in humans
- Toxic effects on livestock and pets
- Additional toxicological data
Dissociation constant
Administrative data
Link to relevant study record(s)
- Endpoint:
- dissociation constant
- Type of information:
- read-across from supporting substance (structural analogue or surrogate)
- Adequacy of study:
- key study
- Justification for type of information:
- REPORTING FORMAT FOR THE ANALOGUE APPROACH
For further information please refer to read across justification in IUCLID section 13. - Reason / purpose for cross-reference:
- read-across source
- Dissociating properties:
- yes
- No.:
- #1
- pKa:
- 2.16
- Temp.:
- 25 °C
- Remarks on result:
- other: 1st proton
- No.:
- #2
- pKa:
- 7.21
- Temp.:
- 25 °C
- Remarks on result:
- other: 2nd proton
- No.:
- #3
- pKa:
- 12.32
- Temp.:
- 25 °C
- Remarks on result:
- other: 3rd proton
Reference
Description of key information
No experimental determination of the dissociation constants in water was performed for the test materials as it was anticipated that on performance of the test procedures, as detailed in Method 112 of the OECD Guidelines for Testing of Chemicals, 12 May 1981, that the resulting dissociation constants determined would be that of the parent anions only, for which literature values are available. For example, it is anticipated that different types of orthophosphate will demonstrate significantly different pH values in water due to increasing numbers of protons being substituted with the particular cation on titration with acid or base as appropriate, the actual dissociation constants determined for each compound would be common, i.e. that of the triprotic acid anion. Titrations would also be expected to be similar irrespective of the counter ion. Read-across is justified on the basis that phosphoric acid is the parent acid for all inorganic phosphates.
Key value for chemical safety assessment
Additional information
The dissociation of the read-across substance phosphoric acid occurs in three steps. The first dissociation results in the dihydrogen phosphate anion. The second dissociation leads to the hydrogen phosphate anion.Phosphate or orthophosphate anion is the resulting product of the third and last dissociation.For each of the dissociation reaction steps a dissociation constant can be determined. For the first dissociation step the pKa = 2.12, for the second dissociation reaction step the pKa = 7.21 and the third dissociation has a pKa = 12.67. All dissociation constants were determined at a temperature of 25 °C. The dissociation constants show an increase from dissociation step to the next. This effect is due to the former loss of a H proton, resulting in a negatively charged molecule and a higher energy demand for further dissociation steps.
No. |
pKa |
Temperature (°C) |
#1 |
2.16 |
25 |
#2 |
7.21 |
25 |
#3 |
12.32 |
25 |
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