Litmus is a mixture of dyes used as an indicator. It is extracted from which types of plant?
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",
Litmus has the CAS number 1393-92-6 and contains 10 to 15 different dyes. All of the chemical components of litmus are likely to be the same as those of the related mixture known as orcein, but in different proportions. In contrast with orcein, the principal constituent of litmus has an average molecular mass of 3300. Acid-base indicators on litmus owe their properties to a 7-hydroxyphenoxazone chromophore. Some fractions of litmus were given specific names including erythrolitmin (or erythrolein), azolitmin, spaniolitmin, leucoorcein, and leucazolitmin. Azolitmin shows nearly the same effect as litmus. Red litmus contains a weak diprotic acid. When it is