what is the chemical that causes litmus paper to change color. How is litmus paper made?

Answer 1

Litmus is a water-soluble dye extracted from certain lichens and absorbed on to filter paper. The resulting piece of paper becomes a pH indicator (one of the oldest), used to test materials for acidity. Blue litmus paper turns red under acidic conditions and red litmus paper turns blue under basic conditions, the colour change occurring over the pH range 4.5-8.3 (at 25°C). The active ingredient of Litmus is called Erythrolitmin. Low pH value substances are called acids, and high ones are called alkalis.

Answer 2

Litmus is the indicator embedded in the paper. Litmus can change color by interacting with either a base (its blue) or an acid (its red). Litmus can be used in a solution, or soak paper in the litmus and allow to dry.