- Pour water, an acid solution and an alkali solution into test-tubes.
- Add a few drops of litmus solution into each test-tube.
Demonstration of the different colors of litmus
Scientific name: Litmus becomes different colors in the solutions of acids and bases
Wear eye protection and lab gloves. Avoid contact of the acid and base solutions with skin.
Always follow general safety recommendations. Please note that conducting chemistry experiments you must comply with the relevant legal procedures in your country.
C12H7NO3 + OH- → C12H6NO3- + H2O
Litmus is a mixture of different dyes. One of them is 7-hydroxyphenoxazone which has properties of a weak acid. In an acid solution it is present in a red colored protonated form. In a base solution OH-group of 7-hydroxyphenoxazone dissociates and forms H+ ions. The dissociated form of 7-hydroxyphenoxazone is blue. In neutral solutions litmus is violet.