Nomenclature - the Colour Index system

In modern scientific and techno-commercial publications, pigments are frequently discussed using a universally accepted standard coding system known as the Colour Index, which was jointly developed by the Society of Dyers and Colourists in the United Kingdom and the Association of Textile Chemists and Colorists in the United States. The Colour Index identifies each colorant by giving the compound a unique Colour Index name and a Colour Index number. The five or six digit Colour Index number is allocated to a colorant according to its chemical constitution as described in Table 3.1. 

Chemical class Cl numbers Chemical class Cl numbers 

The Colour Index, names for pigments and their abbreviations are shown in Table 3.2. 

For example, phthalocyanine blue has the Colour Index name Pigment Blue 15 (Cl PB 15) and the Colour Index number 74160. 

For distinguishing pigments with the same chemical composition but a small difference in structure, such as the metal or acid used for salt formation, a subdivision has been made by addition of a digit to the Cl name or Cl number after a colon. This is also used to distinguish pigments In which crystal modifications yield products with the same chemical structure but significantly different properties. 

---