litmus


litmus
/lit"meuhs/, n.
a blue coloring matter obtained from certain lichens, esp. Roccella tinctoria. In alkaline solution litmus turns blue, in acid solution, red: widely used as a chemical indicator.
[1495-1505; earlier lytmos < ON litmosi dye-moss, equiv. to lit- color, dye + mosi moss]

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Mixture of coloured organic compounds obtained from several species of lichens.

In the form of a water solution or as litmus paper, it is the oldest and most-used indicator of whether a substance is an acid or a base. It turns red or pink in acid solutions and blue or purple-blue in alkaline solutions.

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      mixture of coloured organic compounds obtained from several species of lichen that grow in The Netherlands, particularly Lecanora tartarea and Roccella tinctorum. Litmus turns red in acidic solutions and blue in alkaline solutions and is the oldest and most commonly used indicator of whether a substance is an acid or a base.

      Treatment of the lichens with ammonia, potash, and lime in the presence of air produces the various coloured components of litmus. By 1840 litmus had been partially separated into several substances named azolitmin, erythrolitmin, spaniolitmin, and erythrolein. These are apparently mixtures of closely related compounds that were identified in 1961 as derivatives of the heterocyclic compound phenoxazine.

      Archil ( orchil, or orseille) is a mixture of dyes similar to litmus that are obtained from the same lichens by a different method. The manufacture of archil, which produces a violet shade on wool or silk, was introduced into Europe from the Orient about 1300.

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Universalium. 2010.

Look at other dictionaries:

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  • 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},… …   The Collaborative International Dictionary of English

  • litmus — blue dye stuff obtained from certain lichens, early 14c., from M.Du. lijkmoes (Du. lakmoes), from lac (see LAC (Cf. lac)) + moes pulp. Another theory is that it represents O.N. litmose, lit. lichen for dying, from O.N. lita to dye, to stain, from …   Etymology dictionary

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  • litmus — ► NOUN ▪ a dye obtained from certain lichens that is red under acid conditions and blue under alkaline conditions. ORIGIN from Old Norse words meaning dye and moss …   English terms dictionary

  • litmus — [lit′məs] n. [ON litmose, lichen used in dyeing < litr, color (akin to Goth wlits, face < IE * witu , appearance < base * wel , to see > L voltus, expression, Welsh gweled, to see) + mosi, MOSS] a purple coloring matter obtained from… …   English World dictionary

  • litmus — noun Etymology: Middle English litmose, of Scandinavian origin; akin to Old Norse litmosi herbs used in dyeing, from litr color (akin to Old English wlite brightness, appearance) + mosi moss; akin to Old English mōs moss Date: 14th century 1. a… …   New Collegiate Dictionary

  • litmus — noun a) A dyestuff extracted from certain lichens, that changes color when exposed to pH levels greater than or less than certain critical levels. b) A simple test of acidity in a liquid using litmus, usually in the form of litmus paper. Syn:… …   Wiktionary

  • litmus — /ˈlɪtməs / (say litmuhs) noun a colouring substance obtained from certain lichens, especially Roccella tinctoria. In alkaline solution litmus turns blue, in acid solution red; hence it is widely used as an indicator, especially in the form of… …   Australian English dictionary

  • litmus — n. a dye obtained from lichens that is red under acid conditions and blue under alkaline conditions. Phrases and idioms: litmus paper a paper stained with litmus to be used as a test for acids or alkalis. Etymology: ME f. ONorw. litmosi f. ON… …   Useful english dictionary


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