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EC number: 234-525-3 | CAS number: 12007-99-7
- 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
- Endpoint:
- hydrolysis
- Data waiving:
- study scientifically not necessary / other information available
- Justification for data waiving:
- the study does not need to be conducted because the substance is highly insoluble in water
Cross-referenceopen allclose all
- Reason / purpose for cross-reference:
- data waiving: supporting information
Reference
- Endpoint:
- water solubility
- Type of information:
- other: review of literature
- Adequacy of study:
- key study
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- data from handbook or collection of data
- Qualifier:
- no guideline followed
- Principles of method if other than guideline:
- Molecular Orbital Theory of metal-metal bonds
- GLP compliance:
- no
- Remarks:
- (Theoretical consideration of chemical structure)
- Type of method:
- other: literature review
- Key result
- Remarks on result:
- not determinable
- Remarks:
- Based on molecular orbital theory, the bond energy of the B-B bonds is too high to be cleaved by solvation. Only hydrolysis in strong acid would slowly cleave the B-B bonds. Therefore, CaB6 is insoluble in water.
- Conclusions:
- Calcium hexaboride is insoluble in water.
- Executive summary:
Based on a review of literature and the crystal structure of calcium hexaboride, water solubility is not a relevant property. The structure of calcium hexaboride is a covalently linked lattice of hexaboride unit interspersed with calcium ions [Ca(II)]. The bond strength of the boron-boron connections is too great for dissolution or hydrolysis in aqueous solution. After ligand-exchange by protons, the crystalline lattice may be disrupted more easily. Acid-mediated hydrolysis can then occur in non-oxidizing mineral acid solution. This study is based on a review of the scientific literature and sound scientific concepts. It is deemed reliable with restrictions, and is suitable for Risk Assessment, Classification & Labelling, and PBT Analysis.
Water solubility of calcium hexaboride is not a relevant property. Rather than being an ionic solid consisting of calcium and hexaboride ions, calcium hexaboride consists of calcium ions [Ca(II)] packed into an anionic crystalline 3-D polymeric lattice formed by hexaboride. As such, calcium may be exchanged with other cations, but the hexaboride lattice will remain intact. The crystal structure of calcium hexaboride consists of calcium cations in a close packed 3-D structure of covalently-linked octahedral hexaboride units (1). “The presence of a strong bond between boron atoms in hexaborides creates a strong frame work of boron atoms, in which each boron atom is bonded to four neighboring boron atoms in the same octahedron and to one boron atom in the next octahedron. (3 1/3 bonding electrons per boron)” (2). This results in seven intra-unit bonding orbitals forming each octahedral hexaboride and six outwardly directed orbitals forming one bond with each of six neighboring octahedral hexaboride units, for each boron in an individual octahedron (3). The result is a bond dissociation energy of ca -6.5 eV for each B-B bond within a hexaboride octahedron, a -13 eV orbital consisting of two electrons shared six ways and six hexaboride-hexaboride bonds connecting the octahedral with a dissociation energy of ca. -8 eV (3). These energies can be compared to the 4.40 eV bond energy for the covalent C-H bond and a 3.91 eV bond energy for the covalent C-C bond (4). “Dissolution” would therefore involve the breaking of strong covalent bonds within the hexaboride 3-D lattice, i.e. hydrolysis, rather than the disruption of weaker intramolecular ionic involved in dissolving ionic salts or organic molecules. However, sufficient energy to do this is not available in aqueous solution. In order to dissolve one the hexaboride, more energy is required than for water to break all C-C and C-H bonds in ethane. As ethane is not atomized in water, it is safe to assume that a hexaboride octahedron would not be cleaved from the crystal lattice in water.
Calcium hexaboride will dissolve slowly in non-oxidizing acids (1, 2). The proposed mechanism is intrusion of protons into the lattice which possibly forces the adoption of a Hexaboride Lanthanum type electronic structure. This is followed by more proton intrusion and subsequent loss of Ca(II). Lastly, water intrudes and dissolution occurs. It is unclear exactly when the boride octahedral is broken down or when oxidation of released boron occurs.
1. G. Raynor, K. Trask. Chemistry and Applications of Calcium and Potassium, Rev Ed., Academic Studio, New York, NY, 2016, p. 23.
2. G.V. Samsonov, B. Paaderno. Borides of Rare Earth Metals, Academy of the Sciences, SSR Kiev, 1961, p. 10-11.
3. K. Schmitt, C. Stückl, H. Ripplinger, B. Albert. Crystal and electronic structure of BaB6 in comparison with CaB6 and molecular [B6H6]2 -. Solid State Sci. 2001, vol. 3, pp. 321-32.
4. S. J. Blanksby, G.B. Ellison. Bond Dissociation Energies of Organic Molecules. Acc. Chem. Res. 2003, vol. 36, no. 4, pp. 255–2637.
- Reason / purpose for cross-reference:
- data waiving: supporting information
Reference
- Endpoint:
- melting point/freezing point
- Type of information:
- not specified
- Adequacy of study:
- key study
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- data from handbook or collection of data
- Principles of method if other than guideline:
- no data
- GLP compliance:
- no
- Type of method:
- other: no data
- Key result
- Melting / freezing pt.:
- 2 235 °C
- Remarks on result:
- other: no data on pressure
- Conclusions:
- The melting point of CaB6 is reported as 2235 °C.
- Executive summary:
The melting point of CaB6 is reported as 2235 °C. Because this data is available in a handbook, it is considered reliable with restrictions.
Data source
Materials and methods
Results and discussion
Applicant's summary and conclusion
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