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

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

References

1. Willmes, Arnold (2007). Taschenbuch Chemische Substanzen. Frankfurt am Main. ISBN 978-3817116621.{{cite book}}: CS1 maint: location missing publisher (link)
2. Tashiro’s indicator solution in ethanol
3. SDS
4. Tashiro’s indicator solution in methanol