Title: Litmus

Additional Names: Lacmus; tournesol; turnsole; lacca musica; lacca coerulea

Literature References: Mol wt about 3300. Blue coloring matter from various species of lichens, particularly Variolaria, Lecanora, and Roccella. Habit. Scandinavia, shores of Mediterranean, Azores, California, East India, Madagascar. Constit. Chiefly azolitmin and erythrolitmin combined with alkalies: lecanoric acid, orcein, erythrolein. Manuf almost exclusively in Holland. Structure studies: Beecken et al., Angew. Chem. 73, 665 (1961). Contains in small amounts a,b,g-amino and hydroxyorcein.

Properties: Blue powder, lumps or cubes. Partly soluble in water or alcohol.

Use: As acid-base indicator; pH: 4.5 red, 8.3 blue. For preparing litmus papers; in microscopy to color culture media for diagnostic purposes. Has been used for coloring beverages.