Green, Acid Azine

Nonchelating dyes include basic triphenylmethane dyes (e.g., Brilliant Green, Malachite Green, Crystal Violet), xanthene dyes (e.g., Rhodamine B, Rhodamine 6G), azine dyes (e.g., Methylene Blue), and acid dyes (e.g., Eosin, Erythrosin). These are intensely colored and when paired with an oppositely charged analyte ion lead to high sensitivities. 

Here also the acid radical is combined with the azine group, and the amido-groups only form salts in presence of an excess of acid, the change being accompanied by a characteristic change of colour through blue to green. 

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