Table 5.1 A range of visual indicators for acid-base titrations
Indicator pKIn Low pH colour High pH
colour
Experimental
colour change
range/pHcresol red ca.1 red yellow 0.2–1.8
thymol blue 1.7 red yellow 1.2–2.8
bromo-phenol blue 4.0 yellow blue 2.8–4.6
methyl orange 3.7 red yellow 3.1–4.4
methyl red 5.1 red yellow 4.2–6.3
bromo-thymol blue 7.0 yellow blue 6.0–7.6
phenol red 7.9 yellow red 6.8–8.4
phenolphthalein 9.6 colourless red 8.3–10.0
alizarin yellow R ca. 11 yellow orange 10.1–12.0
nitramine ca. 12 colourless orange 10.8–13.0
(a) phenolphthalein