From Wikipedia, the free encyclopedia   (Redirected from Litmus
test) Jump to: navigation, search For other uses, see Litmus
(disambiguation). Litmus powder Chemical structure of
7-hydroxyphenoxazone, the chromophore of litmus components
Litmus is a water-soluble mixture of different dyes extracted
from lichens, especially Roccella tinctoria. It is often
absorbed onto filter paper to produce one of the oldest forms of
pH indicator, used to test materials for acidity. Blue litmus
paper turns red under acidic conditions and red litmus paper
turns blue under basic (i.e. alkaline) conditions, with the
color change occurring over the pH range 4.5-8.3 at 25 °C
(77 °F). Neutral litmus paper is purple.[1] Litmus can also be
prepared as an aqueous solution that functions similarly. Under
acidic conditions, the solution is red, and under basic
conditions, the solution is blue.  The litmus mixture has the
CAS number 1393-92-6 and contains 10 to 15 different dyes. Most
of the chemical components of litmus are likely to