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EC number: 215-236-1 | CAS number: 1314-56-3
- 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
Hydrolysis
Administrative data
Link to relevant study record(s)
Description of key information
Diphosphorus pentaoxide is extremely hygroscopic and reacts violently with water to form an aqueous solution of different phosphorus oxyacids. The proportion of the oxyacids as well their further hydrolysis depends on the way of preparation of the sample and on several physical parameter (van Wazer page 453) like temperature, pH value and concentration.
The end product of the hydrolysis is the orthophosphoric acid, whereby the hydrolysis and the main product of the rapid hydrolysis is tetrametaphosphoric acid which is quite stable under conditions relevant for ecotoxicological studies like low concentration and quite neutral pH value.
Hazardous reaction:
Especially fine powder of the hexagonal form can react explosively with water, forming a mixture of acidly phosphorus oxyacids. The intensity of the reaction leads to the proposal of a supplemental hazard classification EUH014 (reacts violently with water) for completion of the Annex VI part 3 classification (see chapter 2).
Environment:
Hydrolysis of P2O5 in water under conditions relevant for ecotoxicological studies (100mg/L, 25°C) leads to slightly acidic solutions (pH 3.6) with the main product oftetrametaphosphoricacid. Further hydrolysis within the time frame of ecotoxicological studies is insignificant.
Oral exposure:
Hydrolysis of P2O5in dilute hydrochloric acid (0.5%) under conditions relevant for toxicological studies (37°C) leads to solutions that undergo further hydrolysis. After about an hour the main products are mono- and diphosphoric acid.
Key value for chemical safety assessment
- Half-life for hydrolysis:
- 0.01 min
- at the temperature of:
- 25 °C
Additional information
Diphosphorus pentaoxide is hygroscopic forming with water an aqueous solution of phosphorus oxyacids (primary hydrolysis) which are subject to further (secondary) hydrolysis to the end product phosphoric acid, H3PO4.
The reactivity of the primary hydrolysis differs with the crystalline modification, whereby the hexagonal form reacts immediately or almost explosively to a clear solution, the orthorhombic(R-)form swells slowly to a milky sol or a suspension and the orthorhombic (S-)form builds with a limited amount of water a gel changing with time or dilution into a clear solution.
The less soluble parts consist of high molecular phosphoric acids, which can also be achieved by improper circumstances in the solution process, like a small surface or insufficient stirring,
The hydrolytically scission of the P-O-P linkages depends in general from the following factors, and the given magnitudes (by van Wazer) are representative for the transformation products of the secondary hydrolysis.
Factor |
Approximate effect on rate |
1. Temperature |
105-106faster from freezing to boiling |
2. pH |
103-104slower from strong acid to base |
3. Enzymes |
As much as 105-106 faster |
4. Colloidal gels |
As much as 104-105 faster |
5. Complexing cations |
Very many-fold faster in most cases |
6. Concentration |
Roughly proportional |
7. Ionic environment in the solution |
Several-fold change |
These factors lead to a fluctuation of the half live time of different oxyacids from several minutes to some years.
Usually the commercial grade of phosphorus pentaoxide belong to the M form, consisting of P4O10 molecules forming with water immediately a clear aqueous solution of different phosphorus oxyacids according to a well investigated reaction scheme.
In the only possible first step of the hydrolysis an ultraphosphate ( H2P4O11) is produced. This unstable ultraphosphate break down to give either tetrametaphosphoric acid (H4P4O12) , a four unit cyclic molecule, or the iso tetrametaphosphoric acid (H2P3O9)with an end group attached on a three unit cyclic molecule.
The tetrametaphosphoric acid is the main product of the rapid primary hydrolysis and quite stable under relative mild conditions whereby the branching point on the substituted trimetaphosphoric acid undergoes further rapid degradation eiher in tetrapolyphosphoric acid ( H6P4O13) or trimetaphosphoric acid ( H3P3O9) and isotetrapolyphosphoric acid ( H6P4O13). The later one also has a branching point and should as well as the trimetaphosphoric acid rapidly undergo further degradation into tri polyphosphoric acid . Further reactions of the remaining chain polyphosphoric acids are leading quite slowly to pyrophosphoric acid ( H4P2O7) and finally orthophosphoric acid ( H3PO4).
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