Other Notes Literature for Patent Blue Violet discusses two dyes which are very similar, Color Index Numbers 42045 and 42051. Structurally they differ with regard to the substituents on one of the aromatic rings. C.I. 42045 is 2,4-disulfo-substituted while C.I. 42051 is 2,4-disulfo-5-hydroxy-substituted. This is the latter form. |