Material Choice
One of the most commonly used chemical compounds in the home is pigments, substances that color materials. There are a considerable number of different pigments, but among them, we should highlight titanium dioxide as the compound we use most often. Titanium dioxide is used as a food coloring, so it is actively used in a variety of food products, including tubes of toothpaste. More specifically, titanium dioxide gives the material a glossy white glow that shimmers perfectly when exposed to sunlight. This is why the pigment can be used wherever a product needs to have a rich white color — in addition to toothpaste and whitening powders; this includes paper, ink, cosmetics, and construction paints. Notably, titanium dioxide is a food coloring so it can be found in foods. These include candy, cream and milk, and culinary sauces. The identification number of titanium dioxide as a certified food coloring is E171.
Chemical Composition
Titanium dioxide has the chemical formula TiO2, which is an amphoteric oxide of the tetravalent metal titanium. There is an ionic bond between the atoms in the compound, and the approximate molecular weight of the substance is 80 g/mol. Chemically speaking, titanium dioxide is amphoteric, which means it can exhibit both acidic and basic properties. This increases the variety of possible applications of the material.
It is noteworthy that titanium dioxide in its pure form is a colorless crystal, so it is a legitimate question to determine why this substance is used as a white pigment. Titanium dioxide is believed to have excellent optical characteristics, so when light rays hit the substance, it reflects them strongly, giving the colored material a bright gloss (EuroChlor, 2018). The ability to dye materials white is primarily due to their unique chemical structure. The titanium dioxide molecule is constructed in such a way that when light hits it, diffuse scattering occurs; in other words, visible light is reflected from the pigment (The Chemours Company, 2019). It is for this reason that a film of such pigment will appear white because it reflects all wavelengths.
Dangers
It is worth mentioning that titanium dioxide began to be used in industry as an alternative to lead oxides. Lead oxides are also bleaching pigments, but they have been shown to be hazardous to health, so they have been banned from use (NJ Health, 2017). For a long time, titanium dioxide was considered a relatively harmless substance and could only cause short-term effects, whether skin, nose, or throat irritation. However, more recent studies have shown that titanium dioxide can cause cancer when inhaled and thus is a suspected carcinogen, which has been proven in animals (NJ Health, 2017). There is no definitive data on the harmful effects of this substance on humans, but the presence of carcinogenicity for animals makes it necessary to be more careful about the substance.
Alternatives
Since titanium dioxide does not give the material any unique color but instead colors it plain white, a considerable number of alternatives can be used instead of titanium dioxide. These include synthetic silicates, calcium carbonate, and barium sulfate, as well as an aqueous solution of kaolin (Hilton, 2019). It is clear that the use of alternatives is associated with individual technical difficulties, but their diversity allows us to choose the best option.
References
The Chemours Company. (2019). Titanium dioxide for coatings [PDF document].
EuroChlor. (2018). Titanium dioxide: The whitest white. EuroChlor.
Hilton, S. (2019).Is there a true substitute for titanium dioxide?AgchemiGroup.
NJ Health. (2017). Hazardous substance fact sheet [PDF document].
NJ Health. (2017).Hazardous substance fact sheet[PDF document].