Chrominfo: pH range and color change of indicators used in titration

Compounds that change color when exposed to acidic or basic solutions are known as indicators. Color indicators are widely used to detect pH and can be added to the reaction mixture to determine the titration endpoint or equivalence point.

A variety of indicators are used in different types of titrations, including acid-base, redox, precipitation, and complexometric. Each has its pKa, pH range, and produces a different color at different pH levels.

Table of Contents:

1. Acid base indicators
2. Metal indicators
3. Non aqueous indicators
4. Redox indicators
5. Adsorption and miscellaneous indicators

In chemistry, there are three types of indicators: natural indicators, artificial indicators, and olfactory indicators, while artificial and natural indicators are the two most commonly used forms.

Here are some common indicators are listed in table form along with their pH range, and color change under acidic, basic, and neutral environments.

List of indicators used in acid-base titration:

Name of Indicator	Useful pH Range	Color Change
Bromocresol Green	3.6 to 5.2	Yellow to blue
Bromocresol Purple	5.2 to 6.8	Yellow to bluish-violet
Bromophenol Blue	2.8 to 4.6	Yellow to bluish-violet
Bromothymol Blue	6.0 to 7.6	Yellow to blue
m-Cresol	1.2 to 2.8 and 7.6 to 9.2	Red to yellow and yellow to violet
Cresol Red	0.2 to 1.8 and 7.2 to 8.8	Red to yellow and yellow to violet-red
Dimethyl Yellow	2.8 to 4.6	Red to yellow
2-4 Dinitrophenol	2.8 to 4.4	Colorless to yellow
Methyl Orange	2.9 to 4.6	Red to yellow
Methyl Red	4.2 to 6.3	Red to yellow
1-Naphtholphthalein	7.3 to 8.7	Pale red to blue
3-Nitrophenol	6.8 to 8.4	Colorless to yellow
4-Nitrophenol	5.0 to 7.0	Colorless to yellow
Phenolphthalein	8.3 to 10.0	Colorless to red/pink
Phenol Red	6.8 to 8.4.	Yellow to red
Thymol Blue	1.2 to 2.8 and 8.0 to 9.6	Red to yellow and to violet-blue
Thymolphthalein	8.3 to 10.5	Colorless to blue

List of common metal indicators used in complexometric titration:

Name of Indicator	Useful pH Range	Color Change
Calcein	-	Orange-yellow to yellowish red
Calcon	-	Purple red to pure blue
Catechol Violet	0.0 to 8.0	Blue/red to yellow
Dithizone	-	Pink to green
Methyl-thymol Blue	4.0 to 10.0	Red to yellow to blue
Mordant Black II	7.0 to 11.0	Blue to pink
Murexide	6.0 to 13.0	Yellow to reddish-purple to blue-purple
Pyridylazonaphthol	-	Yellow to Red
Sodium Alizarin Sulphonate	3.7 to 5.2	Bluish-red to yellow
Thoron	-	Red to yellow
Xylenol orange	6.4 to 10.4	Yellow to orange-red

List of common indicators used in non-aqueous titrations:

Name of Indicator	Useful pH Range	Color Change
Alkali Blue 6B	9.4 to 14	Red to Blue
Crystal Violet	0.0 to 2.0	Violet (basic), to bluish-green (neutral) to yellowish green (acidic)
1-Naphtholbenzein	8.2 to 10.0	Green (basic) to orange (neutral) to yellow (acidic)
Quinaldine Red	1.0 to 2.2	Magenta to colorless.

List of common indicators used in oxidation and reduction (Redox) titrations:

Name of Indicator	E0, V	Color of oxidized and reduced form
Potassium permanganate (KMnO4)	1.51 V	Purple to colorless
Crystal Violet	0.0 to 2.0	Violet (basic), to bluish-green (neutral) to yellowish green (acidic)
1,10-Phenanthroline iron(II) sulfate complex (Ferroin)	+1.08 V	Red to blue
Ceric ammonium sulphate	-	Pink to very pale blue
Phenanthroline blue	+1.06 V	Deep red to light-blue
Methylene blue	+0.53	Blue to colorless
Safranin T	+0.24	Red-violet to colorless
Barium Diphenylamine-4-Sulphonate	+0.84 V	Colorless to violet
Indigo carmine	+0.29	Blue to colorless

List of common indicators used in adsorption and miscellaneous:

Name of Indicator	Useful pH Range	Color Change
Amaranth	-	Orange-red to yellow
Dicblorofluorescein	5 to 8	Precipitate orange to pink
Starch	-	Colorless to blue
Potassium chromate	6.5 to 10.5	Yellow to reddish brown