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Element Index
Technetium
Tellurium
Thallium
Tin
Titanium
Chemical's truth
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Ricin is a natural poison extracted from the castor oil bean with a quoted LD50 of 20,000 ng/kg. |
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Titanium(IV) oxide
(titanium dioxide, titania)
CAS no: 13463-67-7 Formula: TiO2 Molecular weight: 79.866
Physical Data
Appearance: White tetrahedral crystalline powder. Large crystal (titania) is translucent water-white or with yellowish cast.
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Melting point: 1843°C
Boiling point: ~2700-3000°C
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Density: 4.23 g/cm3 (rutile)
Solubility: -
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Thermodynamic Data
Enthalpy of formation: -944.0 kJ/mol
Gibbs energy of formation: 888.8 kJ/mol
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Entropy: 50.6 J/mol K
Heat capacity: 55.0 J/mol K
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Production and preparation
Occurs in nature as the minerals brookite (othorhombic), anatase (tetragonal), rutile (tetragonal) and ilmenite (FeTiO3). The oxide was first discovered by an amateur chemist, W. Gregor in 1791, from ilmenite, a black iron-containing mineral.
The iron was removed by hydrochloric acid and the residue was the impure TiO2.
Can be prepared by direct combination of titanium and oxygen or reaction of volatile titanium compounds with oxygen (for example, the chloride process).
Due to the presence of impurities, the use of industrial-quality TiO2 as pigments cannot be obtained directly from mineral sources. For example, the use of chloride process to obtain pure TiO2 from the rutile mineral:
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If the mineral source is ilmenite, then more complicated sulfate process will have to use. This method is less preferred due to the production environmentally hazardous iron sulfate waste.
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Behavior and Chemical Properties
The oxide is insoluble in water or dilute acids, but soluble in concentrated sulfuric acid. It has high refractive index in the visible region of the spectrum and hence render its main use as a pigment.
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History and Uses
Due to its inert chemical nature and white coloring durability titanium(IV) oxide's main use are pigments in paints, enamels, lacquers and food industry. In the past, most white paints contain lead, which was a toxic hazard and degraded after a duration of weathering effects
(due to the formation of PbS).
For this reason, since 1920s, most white paints contain the chemically inert TiO2. For example, the tetragonal
anatase is used as exterior white house paints, lacquers, acetate rayon, ink, plastics, paper filings, water paints and shoe witheners. It is also used in welding-rod industry.
The rutile compound is used for welding-rod coating materials, ceramic colorant and as a source for titanium metal production (Kroll method).
Large TiO2 crystals (titania) are used in jewelry. When very pure, these crystals possess properties of a gemstone with brilliance, reflectance and refraction rival, and sometimes greater than,
those of diamonds.
Powdered TiO2 (20-50 nm in sizes) can produce films of high opacity and is used as a UV filter in skin care and cosmetic products.
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Hazard, Storage and Handling
May cause irritation to skins, eyes and respiratory tract. Long-term exposure to the dust may result in mild fibrosis. It is, however, not expected to have any significant health hazard when ingested.
No known toxicological data on normal occupational use.
In case of eye and skin contacts, flush with plenty of water. Seek medical advice if irritation persists.
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Related links
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(Last update: December 2002) |
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