# Color indicators

## Hints

Unbalanced turnover area
If the color intensities of the two indicator forms are very different at the same concentration, then the transition area is asymmetrical with respect to $pH$ = $pKThere$. For two-color indicators, however, the transition area is independent of its total concentration. Single-color indicators (for example phenolphthalein), on the other hand, depend on the concentration with regard to the transition area. So the pink color of phenolphthalein is already at lower levels if it is overdosed $pH$Values ​​visible (see textbooks on quantitative analysis for details).
Influence of the indicator on the $pH$-Value of the solution
Since acid-base equilibria are established automatically in a solution, it does not matter whether an indicator acid or the conjugated indicator base is used. But one must not overlook the fact that the $pH$-Indicators as acids or bases themselves $pH$- slightly affect the value of the solution. When an indicator acid is added, the $pH$Value is reduced, which is generally not measurable if very small amounts are added as intended. During titrations, indicators must not be added in too large quantities so that the titration result is not falsified.