Acid-base Indicator
| Bromophenol blue (pH indicator) | ||
| below pH 3.0 | above pH 4.6 | |
| 3.0 | ↔ | 4.6 |
As an acid-base indicator its useful range lies between pH 3.0 and 4.6. It changes from yellow at pH 3.0 to purple at pH 4.6; this reaction is reversible. Bromophenol blue is structurally related to phenolphthalein (a popular indicator).
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