Titanium dioxide

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Titanium dioxide
Image:Titanium(IV) oxide.jpg
Chemical name	Titanium dioxide Titanium(IV) oxide
Other names	Titania Rutile Anatase Brookite
Chemical formula	Ti O₂
SMILES	O=Ti=O
Molecular mass	79.87 g/mol
Appearance	white solid
CAS number	[13463-67-7]
HS number	Titanium oxides: 2823.00 2823.00.10.000(anatase) 2823.00.90.000(others)
Properties
Density	4.23 g/cm³
Melting point	1850 °C
Boiling point	2500 °C
Solubility	Insoluble
Thermodynamic data
Δ_fH^o_gas]]	−249 kJ/mol
Δ_fH^o_liquid	−879 kJ/mol
Δ_fH^o_solid	−944 kJ/mol
S^o_solid	51 J/mol·K
Hazards
MSDS	External MSDS
EU classification	not listed
NFPA 704	Image:Nfpa h1.png Image:Nfpa f0.png Image:Nfpa r0.png
Flash point	non-flammable
RTECS number	XR2775000
Supplementary data page
Structure and properties	n, ε_r, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds
Other cations	Titanium(II) oxide Titanium(III) oxide Titanium(III,IV) oxide Zirconium dioxide Hafnium dioxide
Disclaimer and references

Titanium dioxide, also known as titanium(IV) oxide or titania, is the naturally occurring oxide of titanium, chemical formula TiO₂. When used as a pigment, it is called titanium white or Pigment White 6.

Titanium dioxide occurs in four forms:

rutile, a tetragonal mineral usually of prismatic habit, often twinned;
anatase or octahedrite, a tetragonal mineral of octahedral habit; and
brookite, an orthorhombic mineral. Both octahedrite and brookite are relatively rare minerals.
Titanium dioxide (B) or TiO₂(B), a monoclinic mineral.

Pure titanium dioxide does not occur in nature but is derived from ilmenite or leuxocene ores. It is also readily mined in one of the purest forms, rutile beach sand.

Titanium dioxide is the most widely used white pigment because of its brightness and very high refractive index (n=2.4), in which it is surpassed only by a few other materials. When deposited as a thin film, its refractive index and color make it an excellent reflective optical coating for dielectric mirrors. TiO₂ is also an effective opacifier in powder form, where it is employed as a pigment to provide whiteness and opacity to products such as paints, coatings, plastics, papers, inks, foods, and most toothpastes. In cosmetic and skin care products, titanium dioxide is used both as a pigment and a thickener, and in almost every sunblock with a physical blocker, titanium dioxide is found both because of its refractive index and its resistance to discoloration under ultraviolet light. This advantage enhances its stability and ability to protect the skin from ultraviolet light. It is also used in resistance-type lambda probes (a type of oxygen sensor).

Titanium dioxide, particularly in the anatase form, is a photocatalyst under ultraviolet light. The strong oxidative potential of the positive holes oxidizes water to create hydroxyl radicals. It can also oxidize oxygen or organic materials directly. Titanium dioxide is thus added to paints, cements, windows, tiles, or other products for sterilizing, deodorizing and anti-fouling properties and is also used as a hydrolysis catalyst. As TiO₂ is exposed to UV light, it becomes increasingly hydrophilic, thus it can be used for anti-fogging coatings or self-cleaning windows. TiO₂ incorporated into outdoor building materials can substantially reduce concentrations of airborne pollutants such as volatile organic compounds and NOx.

TiO₂ is desired as an agent in remediation of wastewater due to several factors.

1. The process occurs under ambient conditions.

2. The formation of photocyclized intermediate products, unlike direct photolysis techniques, is avoided.

3. Oxidation of the substrates to CO₂ is complete.

4. The photocatalyst is inexpensive and has a high turnover.

5. TiO₂ can be supported on suitable reactor substrates.

6. The process offers great potential as an industrial technology to detoxify wastewaters.

The Vinland map, the map of America ("Vinland") that was supposedly drawn during mid-15th century based on data from the Viking Age, has been declared a forgery on the basis that the ink on it contains traces of the TiO₂-form anatase; TiO₂ was not synthetically produced before the 1920s. Recently (1992) a counter-claim has been made that the compound can be formed from ancient ink.

Titanium is used as a white food dye. In that use, its E number is E171. The white color of toothpaste is that of titanium dioxide. It is also used as a tattoo pigment.

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