Litmus paper

Litmus is a mixture which is made from different dyes which can be taken from lichens. It is water-soluble. It is used to tell whether a solution is an acid or an alkali.

Litmus paper being used

Litmus is put onto filter paper. This paper is then called 'litmus paper'. The paper can then be used to give a rough indication of the pH value of a solution. Blue litmus paper will turn red, when acid is present; red litmus paper will turn blue when alkalines are present. At room temperature, this usually happens for pH values between 4.5 and 8.3.

Alternatively, a solution can be prepared which works the same way, but does not need the paper.

Although litmus and litmus paper can determine if any substance is acidic or alkaline, it cannot determine its pH. Universal indicator can be used to determine its exact pH.

Related pages

• pH#Indicators