Litmus

2 definitions found

From The Collaborative International Dictionary of English v.0.48 [gcide]:

  Litmus \Lit"mus\, n. [D. lakmoes; lak lacker + moes a thick
     preparation of fruit, pap, prob. akin to E. meat: cf. G.
     lackmus. See {Lac} a resinous substance.] (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.
     [1913 Webster]
  
     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.
           [1913 Webster]
  
     {Litmus paper} (Chem.), unsized paper saturated with blue or
        red litmus, -- used in testing for acids or alkalies.
        [1913 Webster]

From WordNet (r) 2.0 [wn]:

  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}]