Is Tropaeolin OO vegan?

Tropaeolin OO

Vegan

Tropaeolin OO (Acid Orange 5) is a synthetic azo dye with the formula Na(C6H5NHC6H4N=NC6H4SO3). It is used as a pH indicator, appearing red below pH 1.4 and orange-yellow above pH 3.2. It is produced entirely from synthetic precursors.

Also known as Acid Orange 5, Fast Yellow
CAS number 554-73-4
CI number CI 13080
Last reviewed 3 June 2026

Sources

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