Definition for Indicator
From Biology Forums Dictionary
In terms of titration, an indicator is a substance that undergoes a change in colour when the end-point of a titration is reached. Acid-base indicators are used to signal the end of acid-base titrations.
Acid-base indicators are perhaps the most common types, but different types of indicators are used in precipitation reactions, such as in silver nitrate(V) titrations for chloride ion determination. In reactions where there is a colour change an indicator may not be needed, as in manganate(VII) titrations.
An acid-base indicator is itself a weak acid (or its conjugate base).
An acid-base indicator is a weak acid having a different colour in aqueous solution from its conjugate base.
