Chemistry

Color indicators


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 pHValues ​​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 pHValue 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.


Video: Insert left and right color indicators in ReSound Mini RIE hearing aids (December 2021).