lit·mus /ˈlɪtməs/
 石蕊
 lit·mus /ˈlɪtməs/ 名詞
 石蕊,石蕊素
 Lit·mus n.  Chem. A dyestuff extracted from certain lichens (Roccella tinctoria, Lecanora tartarea, etc.), as a blue amorphous mass which consists of a compound of the alkaline carbonates with certain coloring matters related to orcin and orcein.
 Note: ☞ Litmus is used as a dye, and being turned red by acids and restored to its blue color by alkalies, is a common indicator or test for acidity and alkalinity.
 Litmus paper Chem., unsized paper saturated with blue or red litmus, -- used in testing for acids or alkalies.
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 litmus
      n : a coloring material (obtained from lichens) that turns red
          in acid solutions and blue in alkaline solutions; used as
          a very rough acid-base indicator [syn: litmus test]