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organic dye usually used in the laboratory as an indicator of acidity or alkalinity (see acids and basesacids and bases,
two related classes of chemicals; the members of each class have a number of common properties when dissolved in a solvent, usually water. Properties
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). Naturally pink in color, it turns blue in alkali solutions and red in acids. Commonly, paper is treated with the coloring matter to form so-called litmus paper. Litmus is extracted, chiefly in the Netherlands, from certain lichens (see archilarchil
or orchil
, blue, red, or purple dye extracted from several species of lichen, also called orchella weeds, found in various parts of the world. Commercial archil is either a powder (called cudbear), a pasty mass (called archil), or a drier paste (called persis).
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), which are mashed, treated with potassium carbonate and ammonia, and allowed to ferment. The resulting product is mixed with various colorless substances, such as chalk or gypsum, and is sold in dark blue lumps, masses, or tablets. The active component of litmus, i.e., the part sensitive to acids or bases, is called erythrolitmin.
The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



a dye extracted from certain species of lichen (for example, Roccella tinctoria).

The composition of litmus is complex and has not yet been fully established. The pigment component is the weak acid azolitmin, which yields blue salts. Litmus is used as an indicator: it turns red in an acid medium and blue in an alkaline medium. Test papers impregnated with the dye are generally the form used.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


Blue, water-soluble powder from various lichens, especially Variolaria lecanora and V. rocella ; turns red in solutions at pH 4.5, and blue at pH 8.3; used as an acid-base indicator. Also known as lacmus; lichen blue.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


An organic chemical indicator of acidity or alkalinity; is red in color for pH values below 4.5 and blue above 8.3.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.


a soluble powder obtained from certain lichens. It turns red under acid conditions and blue under basic conditions and is used as an indicator
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
In other--and my--words: So much for the litmus test of a chairman/ CEO split as an indicium of "good governance."
The paper, "When the Destination is Retirement: A Way to Keep Investors' Plans on Track," written by Noelle Fox, senior investment and product analyst at The Principal, is intended to help financial professionals use the litmus test to its fullest capacity.
Cathie: You mean the Norris-Soloway Mobile Litmus Test.
Summary: TEHRAN (FNA)- One of the senior aides of the Iranian President on Wednesday said that Iran views its talks with the Group 5+1 (the five permanent UN Security Council members plus Germany) as a litmus test of the West's good will and honesty.
Here indeed is a litmus test of Welsh Labour's moral integrity..
How he will handle Tibetan residents' grievances against Chinese rule will be the litmus test of whether he is true to his political goal, which China badly needs to attain as it faces widening economic and regional gaps and ethnic tensions.
Romney: No, no.There's no litmus test of that nature.
Those who are practicing, studying, or evading the law will find hours of fun in Stump Your Lawyer, a great litmus test for your knowledge of both useful and not-so-useful topics.
Perhaps nothing better exemplified the district than 7 World Trade Center, whose leasing success many considered a litmus test for the long-term prospects of the district and the need for the millions of squaree feet of new office space planned at the WTC site.
Recognizing that Vichy's struggle "to reconcile paternal power and governmental authority" is readily taken as a marker for "the apotheosis of reactionary measures to reinstate fatherhood as the litmus test of good citizenship" Childers highlights, instead, that in its efforts to refashion the symbols of state control over "nothing less than the nature of government, the shape of the modern family, and the future of the nation," that Vichy's contradictory policies undermined the authority of the same fathers it sought to support (4, 3, 9, 89).
If Casey wins, the lesson for Democrats will be to cede the moral ground to Republicans, and abandon any litmus test of support for social liberties.