Turmeric as indicator | Acids & Bases | Chemistry

Watch how a water based solution of turmeric, a common South Asian cooking spice, can be used as an acid-base indicator. Turmeric only changes colour in the presence of a base, and not in the presence of an acid. An indicator is a substance that changes its colour depending on the pH value of a liquid. Bases such as a soap solution have a pH value greater than 7, whereas acidic liquids like lemon juice have a pH value less than 7. The normally yellow turmeric changes to red-orange when dropped into soap solution, indicating that the soap solution is basic. When acidic lemon juice is slowly added to this, the red-orange gradually weakens and the original yellow is seen again, showing that the acidic lemon juice reacted with the basic soap solution, and turned the liquid to neutral