Intermediate Topic 708 of 1102 Inorganic Chemistry
Pigments and Dyes
Inorganic pigments such as titanium dioxide and Prussian blue give color to materials.
In-depth explanation of Pigments and Dyes
Inorganic pigments are insoluble, finely divided coloured solids used in paints, plastics, inks and ceramics, unlike organic dyes, which dissolve. Their colour comes from electronic transitions, often charge transfer between metal ions and ligands. Titanium dioxide, TiO2, is the most widely used white pigment because its high refractive index scatters light strongly, giving brightness and opacity. Iron oxides give red, yellow and brown colours, and Prussian blue gives deep blue. Their stability to light and heat is valued, although some contain toxic metals such as cadmium and lead.
Going deeper: Pigments and Dyes
Key ideas: Pigments are insoluble particles that color by dispersion (TiO2 white, Fe2O3 red, Prussian blue Fe4[Fe(CN)6]3, ultramarine, chrome yellow PbCrO4, Cr2O3 green), whereas dyes dissolve and bind to fibres. Color arises from d-d or charge-transfer transitions in inorganic pigments, and conjugated pi systems in organic ones. TiO2 has a high refractive index near 2.7, giving opacity. Modern ones replace toxic lead and cadmium.
Common mistakes and connections: Students use pigment and dye interchangeably, but solubility and application differ. Color of a pigment may change with particle size or crystal form (rutile versus anatase TiO2). Lead and chromate pigments are toxic and restricted. Links to colored ions, charge transfer, conjugation and light absorption.
Visualization of Pigments and Dyes
Absorption spectrum of a blue pigment: it absorbs orange-red light near 640 nm and reflects blue, as in copper phthalocyanine or Prussian blue. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Titanium dioxide is used in white paint and in sunscreens, where it scatters and absorbs ultraviolet light.
Frequently asked questions about Pigments and Dyes
What is Pigments and Dyes?
Inorganic pigments such as titanium dioxide and Prussian blue give color to materials.
Is Pigments and Dyes a beginner, intermediate or advanced topic?
Pigments and Dyes is a intermediate topic in Inorganic Chemistry. It builds on the vocabulary of beginner topics in this area.
What should I learn before Pigments and Dyes?
Study these earlier topics in Inorganic Chemistry first: Cisplatin, Qualitative Analysis of Cations, Qualitative Analysis of Anions.
What comes after Pigments and Dyes?
The next topics in Inorganic Chemistry are Ceramics and Superconductors.
Can I practise Pigments and Dyes with quizzes?
Yes. The interactive lesson includes a self-check question on Pigments and Dyes, and the Inorganic Chemistry quiz draws on every topic in this area.
Where Pigments and Dyes fits in Inorganic Chemistry
Pigments and Dyes is topic 93 of 113 in Inorganic Chemistry.