pH and universal indicator

A universal indicator is a mixture of a few other types of indicators. It may be used in the form of a solution or a paper. This indicator turns into different colours when added to different substances. Every colour will correspond to a pH value from 0 to 14. The only disadvantage of the universal indicator is that it can only give the approximate pH value of a solution.

The picture below shows how the indicator works. (Please click on the image if it is not clear enough.)


Acidic mixtures will have a pH value lesser than 7, while alkaline mixtures would have pH value of more than 7. Neutral mixtures will have a pH value of 7, meaning that they are neither alkali nor acid.

In order to get the accurate pH value of a substance, a pH meter can also be used. The electrode is dipped into the solution and the pH value is read directly from the meter.