Redox indicators are colorimetric reagents that undergo a distinct color change at specific electrode potentials, categorized into internal, self, and external indicators. Internal indicators exhibit different colors in oxidized and reduced forms, self indicators are strongly colored titrants, and external indicators react with titrated substances. Their applications include pharmaceutical analysis, inorganic and organic compounds determination, and assessing water quality.

1. Redox Indicators

2. INDICATORS

3. Oxidation/reduction (redox) indicators are colorimetric
reagents which show a distinct color change at a specific
electrode potential.
Examples: Anilinic acid, Diphenylamine, m-cresol-indophenol,
Methylene blue & Nile blue

4. There are 3 types of indicators
Internal or Redox Indicator
Self Indicators
External Indicators

5. Internal Indicators
A redox indicator is a compound,
which exhibits different color in
oxidized and reduced forms.
In(ox)+ne- ↔ In(red)
In(red) ↔ In(ox)+ne-
Indicator name Color change
Oxidized Reduced
1.Nitroferroin
2.Ferroin
3.Diphenylamine Sulphonic
acid
4.Diphenyl amine
5.Starch Iodine
6.Methyl Blue
Pale-blue
Pale-blue
Red-violet
Violet
Blue
Blue
Red
Pale-blue
Colorless
Colorless
Colorless
Colorless

6. Self Indicators
• Titrant itself may be so strongly
colored after the end point, in
that case, titrant acts as a self
indicator.
• One drops of KMnO4 imparts
visible color change to “n” ml
of solution.
• e.g.KMnO4(pink),Iodine(brown)
External Indicators
• They are based on some
visible reactions with titrated
substances along with suitable
reagents.
• e.g. Potassium Ferricyanide
use in titration of Fe2+ and
Cr2O7
2-

7. Potentiometric Methods
• It is a physio-chemical method used for titration of dilute solutions as
well as colored solutions and if there is no suitable end point detection
method is available

8. APPLICATIONS

9. • Redox titration is employed in pharmaceutical analysis, such as the detection of
valganciclovir hydrochloride (VLGH) in tablets and pure medications
• To analyze the wide range of inorganic analytes.
• For the determination of organic compounds.
• This reaction, for instance, is used to determine the chemical oxygen demand of both natural
and waste water.
• Many chemicals like caustic soda and chlorine can be produced by using redox
reaction.
• Galvanization process involves redox reaction.
• Used in the food industry to determine the concentration of vitamin E and C or the
amount of salt and sugar in food goods.
• Evaluating the chlorination of public water sources.