Tashiro's indicator
Tashiro's indicator is a pH indicator (pH value: 4.4–6.2), mixed indicator composed of a solution of methylene blue (0.1%) and methyl red (0.03%) in ethanol or in methanol.
| Tashiro's indicator (pH indicator) | ||
| below pH 4.4 | above pH 6.2 | |
| 4.4 | ⇌ | 6.2 |
It can be used for the titration of ammonia in Kjeldahl analysis.
Colours
- In acids: violet
- At equivalence point (pH 5.2): grey
- In bases: green
Methylene blue functions to change the red-yellow shift of methyl red to a more distinct violet-green shift.