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.[1]
Examples for Tropaeolin dyes
edit| Name | C.I.-Name | Structure | CAS number | Indicator properties | Other uses |
|---|---|---|---|---|---|
| Tropaeolin O
(Resorcingelb) |
Acid Orange 6
Food Yellow 8 |
|
547-57-9 | pH 11.1–12.7 yellow/brown | |
| Tropaeolin OO
(Orange IV) |
Acid Orange 5 | 
|
554-73-4 | pH 1.2–3.2 violet-red/yellow | Dye for wool |
| Tropaeolin OOO1
(Orange I) |
Acid Orange 20 | 
|
523-44-4 | pH 7.6–8.9 yellow/pink | |
| Tropaeolin OOO2
(Orange II) |
Acid Orange 7 | 
|
633-96-5 | pH 7.4–8.6 amber/orange | Dye for wool and silk |
| Tropaeolin D
(Methylorange) |
Acid Orange 52 | 
|
547-58-0 | pH 3.1–4.4 red | Textile dye (USA) |
| Tropaeolin G
(Metanilgelb) |
Acid Yellow 36 | 
|
587-98-4 | pH 1.2–2.3 yellow | |
| Tropaeolin RNP
(Resorcinbraun) |
Acid Orange 24 | 
|
1320-07-6 | – | Coloring cosmetics |