The substances that show different colours in different mediums or the substances that are used to distinguish between an acid and base are called indicators.
Colours of Different Indicators on pH scale
pH value shown by different colours
1. Natural Indicators: The indicators obtained from plants are called natural indicators.
2. Synthetic Indicators: These indicators are manufactured in laboratories.
(a) Methyl Orange
3. Olfactory Indicators: These indicators change their smell when dipped in acid and base.
(a) Onion Extracts
(b) Vanilla Extracts
Table: Indicator Change in acidic medium
Table: Indicator change in basic medium