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EC number: 231-157-5 | CAS number: 7440-47-3
- 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
Appearance / physical state / colour
Administrative data
Link to relevant study record(s)
Description of key information
Chromium metal is a grey, hard, solid, inert, inorganic metal.
Key value for chemical safety assessment
- Physical state at 20°C and 1013 hPa:
- solid
Additional information
Chromium is found in many minerals, but its only commercial source is chromite. In its pure form, chromite comprises 68 % of Cr2O3 and 32 % of FeO. Chromium is found in all phases of the environment, including air, water, soil and living organisms. Chromium is the 21st most abundant element in the Earth’s crust at an average concentration of about 125 ppm. Chromium metal is grey, hard, solid, inorganic metal. It is practically insoluble in water.
Under normal environmental conditions, the chromium on the surface of the metal and chromium-containing alloys such as stainless steel is rapidly converted to the trivalent oxide providing the corrosion resistance. It is well known in metallurgy that on contact with air or other oxygen-containing media, metallic chromium and other metals like iron and nickel rapidly oxidize resulting in a layer of oxides on the surface. This so-called passivation layer is so thin that it does not affect the natural brightness of the metal/alloy, but it very effectively separates the metal/alloy from the surrounding medium. It is continuous, non-porous and insoluble under normal conditions. If it is broken (e. g. by scratching), it is immediately self-healing under the influence of oxygen from air or water. Any effects of other elements are only to influence the effectiveness of chromium in forming or maintaining the film (e. g. nickel promotes re-passivation, especially in reducing environments; and molybdenum stabilizes the passive film in the presence of chlorides). Increasing the chromium content, from the minimum of 10.5 % necessary for ”stainless steel”, to 17 to 20 %, greatly increases the stability of the passive film.
The oxidation states of chromium range from –2 to +6. The important valences are 0, +3 and +6. Elemental chromium(0) does not occur naturally on the Earth but is produced either by metallurgical or electrolytic processes. The trivalent state is the thermodynamically most stable among chromium species. In nature, almost all the chromium exists in trivalent compounds, other forms being mainly of anthropogenic origin. The divalent state is a strong reductant and this form of chromium rapidly decomposes in air or water to form the relatively stable trivalent state. The tetravalent form is only normally encountered as the black magnetic oxide CrO2 used in magnetic recording tapes. The pentavalent state, as the ion (CrO4)3-, is encountered in compounds such as LaCrO4and Ca3(CrO4)2. It is unstable in aqueous solution, disproportionating into chromium(VI) and (III), and is a transient intermediate in the intracellular reduction of the chromate ion, (CrO4)2-. The hexavalent form is the second most stable chromium species. It is a strong oxidant, especially in acidic media. The ease of reduction of hexavalent forms to trivalent increases with increasing acidity. Chromium(VI) occurs only rarely in nature in the mineral crocoite (lead chromate), from which the element was first isolated.
Chromium metal is made mainly by thermal reduction of chromium(III) oxide using aluminium or silicon as reducing agent.
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