Abstract
The pH indicators are used to show sharp color changes at intervals of pH. Natural pigments in plants are highly colored substances and may show color change with variation of pH. An attempt has been made to investigate the indicator activity of water extract of flower and fruit pigments and to replace synthetic indicators, as they cause chemical pollution and are of high cost. The water extract of Caesalpinia sappan, Caesalpiniaceae and Methanolic extract of Dahlia pinnata, Asteraceae showed sharp and intense color change in acidic and basic medium. These herbal indicators are evaluated by using strong acid-strong base, strong acid-weak base, weak acid-strong base and weak acid - weak base titration. In all these titrations, the extract was found to be very useful and accurate for indicating the equivalence point as the synthetic indicators. The isolation of pure compounds possessing indicator properties helps to know the mechanism by which they show indicator properties and new theories of indicators could be established.