What colour does blue litmus paper turn when in contact with acid?
Litmus alkaline conditions, with the color change occurring over the pH range 4.5–8.3 at . Neutral litmus paper is purple. Litmus can also be prepared as an aqueous solution that functions similarly. Under acidic conditions, the solution is red, and under alkaline conditions, the solution is blue. Chemical reactions other than acid-base can also cause a color change to litmus paper. For instance, chlorine gas turns blue litmus paper white – the litmus dye is bleached, because of presence of hypochlorite ions. This reaction is irreversible, so the litmus is not acting as an indicator in this situation. The litmus mixture
Litmus Litmus Litmus is a water-soluble mixture of different dyes extracted from lichens. It is often absorbed onto filter paper to produce one of the oldest forms of pH indicator, used to test materials for acidity. Litmus was used for the first time about 1300 AD by Spanish physician Arnaldus de Villa Nova. From the 16th century on, the blue dye was extracted from some lichens, especially in the Netherlands. Litmus can be found in different species of lichens. The dyes are extracted from such species as "Roccella tinctoria" (South America), "Roccella fuciformis" (Angola and Madagascar), "Roccella pygmaea" (Algeria), "Roccella phycopsis",