Litmus with acids and bases

Demonstration of the different colors of litmus

Scientific name: Litmus becomes different colors in the solutions of acids and bases

YouTube

Лакмус

by Vladimir Kuznetsov

Действие щелочей на индикаторы

by MrVella777

Распознавание целочи, кислоты и воды индикатором

Safety

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.

Reaction formula

C12H7NO3 + OH- → C12H6NO3- + H2O

Step-by-step instruction

  1. Pour water, an acid solution and an alkali solution into test-tubes.
  2. Add a few drops of litmus solution into each test-tube.

Scientific background

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.

Danger:
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Published on 21 May 2015

  • Fire
  • Heating with fire
  • Explosion
  • Poisoned gas
  • Organic
  • Electricity
  • Solution
  • Oxidation reduction
  • Color change
  • Precipitate
  • Gassing
  • Catalyst