Azo Pigment Lakes Salt Type Pigments

In Europe pigments of this type are known as toners , but since this term is differently used elsewhere we refer to them as lakes throughout this book, although a chemically correct description would be salt type pigments . 

Historically, lakes refered to the first type of synthetic organic pigments made from water soluble dyes by precipitation onto alumina hydrate (aluminium hydroxide). 

The organic acid group of Naphthol AS pigment lakes is part of the diazo component a second site for salt formation can be provided by the coupling component. The plastics industry is the main user of such lakes. 

Naphthalenesulfonic acid lake pigments are based on naphthalenesulfonic acid as a coupling component introduction of an additional S03H function as part of the diazo component is possible. 

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