Colour Index Names and Numbers

The Colour Index is used to identify dyes and pigments commercially.  It currently contains around 13,000 chemical structures and 37,000 commercial names.  Definitions of dyes and pigments are given at https://colour-index.com/definitions-of-a-dye-and-a-pigment .

There are two ways that the Colour Index (CI) identifies materials:

• the CI generic name, e.g. Solvent Red 111
• the CI constitution number, e.g. 60505

Both the name and the number refer to a single substance of known structure, which can be identified either through an internet search, or the most reliable way is to subscribe to the Colour Index, which is run by the Society of Dyers and Colourists (SDC) in the UK,  and the American Association of Textile Chemists and Colourists (AATCC), for more information see the website at https://colour-index.com/ .

In terms of identifying chemicals for CLP or Safety Data sheet purposes, the CI number is sometimes considered acceptable for identifying the chemical, and in fact the CI number is use by the INCI system when dyes or pigments are used in cosmetics.  (The INCI system is used for cosmetics ingredients in the UK, EU, USA, Canada etc, and not currently discussed in the knowledgebase as cosmetics are not included under CLP).

However, it is considered best practice for CLP labelling to identify a dye or pigment by the EC number and/or CAS number where you know what these are, as the chemical structure is available freely for substances identified using these numbering systems, whereas the structure of chemicals with CI constitution numbers may only be available to CI subscribers.

The CI name is considered acceptable as a means of identifying a dye or pigment product, whether it is a substance or a mixture, and is often much shorter and more memorable than the chemical substance name.