Acid Alkali Indicators or pH Indicators

Merck offers a wide range of pH indicators for a multitude of different applications. An acid-alkali indicator or pH indicator is a coloring agent, usually a weak acid or base, which changes its color in response to the pH value of an aqueous solution (i.e. in response to a change in the hydrogen ion concentration).

Laboratories use pH indicators mainly to determine the extent of reactions, e.g. to indicate the endpoint of an acid-base titration. In order to accurately determine the point when the acid-base reaction is completed, an indicator is needed that shows a distinct, easily observable color change over a suitable pH transition range that encompasses the pH of the titrated solution at the equivalence point.

In Merck’s comprehensive portfolio of pH indicators, you will certainly find the reagent with just the right properties for your application. Our convenient pH Indicator Selector will assist you: Simply enter the pH value required, and this clever tool gives you an overview of all suitable indicators together with color details, transition intervals and other useful information.