Acid–base indicators
Transition ranges, pKa values, and the colour of each form. The solution colours on the lab bench are computed from these forms’ absorption bands.
| Phenolphthalein | 8.2–10 | 9.3 | colourless → pink |
|---|---|---|---|
| Bromothymol blue | 6–7.6 | 7.1 | yellow → blue |
| Methyl orange | 3.1–4.4 | 3.46 | red → yellow |
| Methyl red | 4.4–6.2 | 5 | red → yellow |
| Bromocresol green | 3.8–5.4 | 4.7 | yellow → blue |
| Phenol red | 6.8–8.4 | 7.9 | yellow → red |
| Thymol blue | 1.2–2.8, 8–9.6 | 1.7, 8.9 | red → yellow → blue |