Classification of Dyes by Use or Application

Usage Classification. It is advantageous to consider the classification of dyes by use or method of application before considering chemical structures in detail because of the dye nomenclature and jargon that arises from this system. 

Table 1 contains a state classification in terms of the more chemically-physically motivated language often used in the literature. Note that the entries in the different sections can in fact occur in almost arbitrary combinations, for example a charge-transfer excited state can be single reference dominated by single excitations (a state often occurring lowest in dyes) or one can have a high-spin Rydberg state, and so on. The last colmnn contains theoretical issues that may be applicable in particular cases. 

There are, of course, many varieties in each of these chemical classifications, so that the result is hundreds of individual dyes each with its own specific characteristics for hue and use on substrates. Dyers have arranged this very complex and large group of chemical products into ten categories arranged by the method of application to the fiber or substrate acid dyes, azoic dyes, basic dyes, direct dyes, disperse dyes, reactive dyes, solvent dyes, sulfur dyes, vat dyes, and mordant dyes. It is in these categories that dyestuffs are discussed in the trade. 

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