Titanium dioxide
[CAS# 13463-67-7]

Identification

• Classification: Inorganic chemical industry >> Inorganic salt >> Oxides of rare earth metals, yttrium or scandium
• Name: Titanium dioxide
• Synonyms: Titanium (IV) dioxide; Titania
• Molecular Formula: TiO₂
• Molecular Weight: 79.87
• CAS Registry Number: 13463-67-7
• EC Number: 236-675-5
• SMILES: O=[Ti]=O

Properties

• Density: 4.26 g/mL (Expl.)
• Melting point: 1855 °C (Expl.)
• Boiling point: 2500 - 3000 °C (Expl.)
• Solubility: Insoluble (Expl.)

Safety Data

• Hazard Symbols: GHS08 Warning
• Risk Statements: H351
• Safety Statements: P203-P280-P318-P405-P501

Discovery and Applications

Titanium dioxide, with the chemical formula TiO₂, is a naturally occurring oxide of titanium and one of the most widely used white pigments in the world. It exists in several crystalline forms, the most common of which are rutile and anatase, both of which are significant in industrial applications due to their stability, brightness, and high refractive index. A third, less common form, brookite, is not typically used commercially.

The compound was first identified in the late 18th century. In 1791, the English mineralogist William Gregor discovered the mineral ilmenite, a major source of titanium, in Cornwall, and noted the presence of a new oxide. Later, in 1821, the German chemist Heinrich Klaproth independently isolated titanium dioxide from rutile. Throughout the 19th and early 20th centuries, titanium dioxide remained largely a mineralogical curiosity until its commercial potential as a pigment was realized.

Titanium dioxide began to see large-scale industrial use in the early 20th century when it was introduced as a superior alternative to toxic lead-based white pigments. Commercial production methods include the sulfate process, which uses ilmenite and sulfuric acid, and the chloride process, which involves the reaction of titanium-containing ores with chlorine gas and subsequent oxidation of titanium tetrachloride. Both methods produce highly pure TiO₂ with desirable pigment properties.

One of the most important applications of titanium dioxide is in the production of white pigments for paints, coatings, plastics, inks, and paper. Due to its high refractive index and strong scattering of visible light, TiO₂ imparts whiteness and opacity to materials even at low concentrations. The rutile form, in particular, is preferred for outdoor applications because of its superior UV resistance and weathering stability.

In the field of sunscreens and cosmetics, titanium dioxide is used as a physical UV filter. It reflects and scatters ultraviolet radiation, protecting the skin from harmful sun exposure. Unlike chemical absorbers, it remains on the surface of the skin and does not degrade significantly under sunlight. For cosmetic uses, TiO₂ particles are often milled to nanometer size to reduce the whitening effect while retaining UV protection.

Titanium dioxide is also important in the area of photocatalysis. In its anatase form, TiO₂ acts as a photocatalyst under ultraviolet light, generating reactive oxygen species that can break down organic pollutants. This property has led to its use in self-cleaning surfaces, air and water purification systems, and antibacterial coatings. Photocatalytic TiO₂ coatings have been applied to glass, ceramics, and building materials for pollution control and sanitation.

In the food industry, TiO₂ has been used as a colorant, designated as E171 in the European Union. It provides whiteness and brightness in products such as candies, chewing gum, and baked goods. However, the safety of ingested TiO₂ has been reassessed in recent years. Regulatory agencies have conducted reviews due to concerns over the potential accumulation and toxicity of nanoparticle forms in the body. As a result, the European Food Safety Authority (EFSA) in 2021 declared that titanium dioxide could no longer be considered safe as a food additive, leading to its prohibition in the EU. Other regions have maintained approval while continuing to review emerging data.

Titanium dioxide is generally regarded as biologically inert and non-toxic when used externally, such as in paints and sunscreens. However, occupational exposure to airborne TiO₂ dust, especially ultrafine particles, is subject to regulation due to the risk of respiratory effects. Workplace safety standards recommend the use of personal protective equipment and dust control measures during handling and processing.

In materials science, TiO₂ is utilized in ceramics, glass coatings, dielectric layers in capacitors, and as a precursor for titanium metal production. Its high dielectric constant and corrosion resistance make it suitable for electronic and optical applications.

In summary, titanium dioxide is a versatile and essential compound used across multiple industries, including pigments, cosmetics, photocatalysis, and advanced materials. Its unique optical and chemical properties have made it indispensable for over a century, and ongoing research continues to expand its functionality and address safety and environmental concerns associated with its use.

References

2025. Selective activation of dioxygen to singlet oxygen over La-Si co-doped TiO2 microspheres for photocatalytic degradation of formaldehyde. Journal of Environmental Sciences (China).
DOI: 10.1016/j.jes.2024.04.012

2025. A novel g-C3N4/TiO2 heterojunction for ultrasensitive detection of bisphenol A residues. Food Chemistry.
DOI: 10.1016/j.foodchem.2024.142123

2025. Inhibition of Salmonella typhimurium and Listeria monocytogenes in coconut juice by graphene-doped photocatalyst rGO/TiO2. Food Chemistry.
DOI: 10.1016/j.foodchem.2024.141103