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[1][2][3] or in methanol.[4]
| Tashiro's indicator (pH indicator) | ||
| below pH 4.4 | above pH 6.2 | |
| 4.4 | ⇌ | 6.2 |
Used e.g. for the titration of ammonia in Kjeldahl analysis.
Colours
- In acids: violet
- At equivalence point (pH 5.2): grey
- In bases: green
The function of the methylene blue is thus to change the red-yellow shift of methyl red to a more distinct violet-green shift.
See also
References
- ^ Willmes, Arnold (2007). Taschenbuch Chemische Substanzen. Frankfurt am Main. ISBN 978-3817116621.
{{cite book}}: CS1 maint: location missing publisher (link) - ^ Tashiro’s indicator solution in ethanol
- ^ SDS
- ^ Tashiro’s indicator solution in methanol