Useful pH range and colour change of some indicator dyes
Indicator dye |
Useful pH range |
Colour change acid to alkaline |
Cresol red (pK1) |
02.-1.8 |
Red-Yellow |
Thymol blue (pK1) |
1.2-.2.8 |
Red-yellow |
Bromophenol blue |
3.0-4.6 |
Yellow-Blue |
Bromocresol green |
3.8-5.4 |
Yellow-Blue |
Methyl red |
4.4-6.0 |
Red-Yellow |
Chlorophenol red |
4.8-6.4 |
Yellow-Red |
Bromocresol purple |
5.2-6.8 |
Yellow-Purple |
Bromothymol blue |
6.0-7.6 |
Yellow-Blue |
Phenol red |
6.8-8.4 |
Yellow-Red |
Gresol red (pK2) |
7.2-8.8 |
Yellow-Red |
Thymol blue (pK2) |
8.0-9.6 |
Yellow-Blue |
Phenolphthalein |
8.3-10.0 |
Yellow-Red |
Tolyl red |
10.0-11.6 |
Red-yellow |
Parazo orange |
11.0-12.6 |
Yellow-Orange |
Acyl blue |
12.0-13.6 |
Red-Bule |