Polymorphism in some specific groups of pigments

3 Polymorphism in some specific groups of pigments 8.3.1 Quinacridones 

The synthesis of quinacridone 8-1 was first claimed in a series of papers beginning in 1896 (Niementowski 1896, 1906 Ullman and Maag 1906 Baczynski and Niementowski 1919) all of which later proved to be an angular isomer of the linear compound first prepared in 1935 (Lieberman 1935 Liebermanefa/. 1935). Little was done with the compound until 1955 when Du Pont chemists recognized its polymorphic behaviour and associated favourable photochemical stability (Jaffe 1992). Jaffe has also noted that many acridone derivatives are polymorphic. Additional relevant references may be found in the recent review by Lincke (2000). 

Pigment Number of forms Reference or page number  

Disperse Yellow 42 2 Burkhard et al. 1968 Flores and Jones 1972 Koch et al. 1987a,b 

Pigment Black 31 I and II Hadicke and Graser (1986a) Mizuguchi (1998fc) 

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