Tashiro's indicator explained

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] 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.

See also

• Litmus
• pH Indicator

Notes and References

1. Book: Willmes. Arnold . Taschenbuch Chemische Substanzen. 2007. Frankfurt am Main. 978-3817116621.
2. http://www.sigmaaldrich.com/catalog/product/fluka/36083 Tashiro’s indicator solution in ethanol
3. https://www.carlroth.com/downloads/sdb/en/2/SDB_2624_GB_EN.pdf SDS
4. http://www.sigmaaldrich.com/catalog/product/fluka/35325 Tashiro’s indicator solution in methanol