In this article we are going to have a look at the pH scale and some other simple indicators of acids and alkalis. We can tell if something is acidic, alkaline or neutral by using an indicator. Indicators are substances that show different colours when thay are in acidic or alkaline conditions. Litmus paper is a simple indicator that tells us whether something is acid or alkali. Litmus is red in acids and blue in alkalis. Litmus paper is made from lichens Which have been used t o die cloth for hundreds of years. It can be used as a liquid or paper. The paper is easier and more reliable. It comes as red litmus paper and blue litmus paper. Red litmus paper changes colour from red to blue under alkali conditions but no changes under acidic conditions. Blue litmus paper changes colour from blue to red under acidic conditions but no change under alkaline conditions. So just remember that ref litmus paper changes colour for alkali and blue litmus paper changes colour for acids. However litmus paper only tells us whether something is acid or alkali, but it does not tell us how acidic or alkaline a substance is from this, we have the pH scale and a universal indicator . Universal indicator is a mixture of different indicators or dyes which has many different color changes and so shows us the pH value of the solution.