Tropaeolin is the retained name for some azo dyes from the industrially applied group of acid dyes used as pH indicators. The name is derived from the botanical name Tropaeolum for nasturtiums.
Examples for Tropaeolin dyes NameC.I.-NameStructureCAS numberIndicator propertiesOther usesTropaeolin O (Resorcingelb)Acid Orange 6 Food Yellow 8547-57-9pH 11.1–12.7 yellow/brownTropaeolin OO (Orange IV)Acid Orange 5554-73-4pH 1.2–3.2 violet-red/yellowDye for woolTropaeolin OOO1 (Orange I)Acid Orange 20523-44-4pH 7.6–8.9 yellow/pinkTropaeolin OOO2 (Orange II)Acid Orange 7633-96-5pH 7.4–8.6 amber/orangeDye for wool and silkTropaeolin D (Methylorange)Acid Orange 52547-58-0pH 3.1–4.4 redTextile dye (USA)Tropaeolin G (Metanilgelb)Acid Yellow 36587-98-4pH 1.2–2.3 yellowTropaeolin RNP (Resorcinbraun)Acid Orange 241320-07-6–Coloring cosmetics
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