أكسيد التيتانيوم (الرابع) (الروتيل)

Titanium (IV) dioxide (TiO2), also known as rutile, is one of the best-known compoundsused as a paint pigment. It is ideal for paints exposed to severe temperatures and marineclimates because of its inertness and self-cleaning attributes. It is also used in manufacture ofglassware, ceramics, enamels, welding rods, and floor coverings.
The naturally occurring dioxide exists in three crystal forms: anatase, rutile and brookite. While rutile, the most common form, has an octahedral structure. Anatase and brookite have very distorted octahedra of oxygen atoms surrounding each titanium atom. In such distorted octahedral structures, two oxygen atoms are relatively closer to titanium than the other four oxygen atoms. Anatase is more stable than the rutile form by about 8 to 12 kJ/mol (Cotton, F.A., Wilkinson, G., Murillo, C.A and M Bochmann. 1999. Advanced Inorganic Chemistry, 6th ed, p. 697, New York: John Wiley & Sons) Other physical properties are: density 4.23g/cm3; Mohs hardness 5.8 g/cm3 ( anatase and brookite) and 6.2 g/cm3 ( rutile); index of refraction 2.488 (anatase), 2.583 (brookite) and 2.609 (rutile); melts at 1,843°C; insoluble in water and dilute acids; soluble in concentrated acids.