litmus

[lit-muh s] /ˈlɪt məs/
noun
1.
a blue coloring matter obtained from certain lichens, especially Roccella tinctoria. In alkaline solution litmus turns blue, in acid solution, red: widely used as a chemical indicator.
Origin
1495-1505; earlier lytmos < Old Norse litmosi dye-moss, equivalent to lit- color, dye + mosi moss
Examples from the web for litmus
  • The litmus test is whether you can spot them in advance.
  • Magnum's output will be observed closely and considered by many as a litmus paper for the industry's integrity.
  • Her problem seems to be that she has violated the university's litmus test for what it means to be open-minded.
  • Strategists and donors for both parties should never forget this, and should always choose leadership abilities over litmus tests.
  • Slums are litmus tests for innate cultural strengths and weaknesses.
  • The true litmus test for the value of education is how well it equips us for navigating modern life.
  • Those are the days which would be the litmus test of this administration.
  • She has dipped her pen in venom and written a comedy that would turn a litmus paper pink.
  • The kind of personal ads a publication runs is generally a fairly accurate litmus of its readership.
  • Reality is not a quality you can test with litmus paper.
British Dictionary definitions for litmus

litmus

/ˈlɪtməs/
noun
1.
a soluble powder obtained from certain lichens. It turns red under acid conditions and blue under basic conditions and is used as an indicator
Word Origin
C16: perhaps from Scandinavian; compare Old Norse litmosi, from litr dye + mosi moss
Word Origin and History for litmus
n.

"blue dye-stuff obtained from certain lichens," early 14c., from Middle Dutch lijkmoes (Dutch lakmoes), from lac (see lac) + moes "pulp." Another theory is that it represents Old Norse litmose, literally "lichen for dying," from Old Norse lita "to dye, to stain," from litr "color, dye" (see lit (n.1)) + mos "moss." Yet another idea connects the first element to Middle Dutch leken "to drip, leak" (see leak (v.)).

Whichever was the original word, it probably was influenced by the others. The dye is obtained from certain lichens. It is naturally blue but turns red in acid and is restored to blue by alkalis. Figurative use of litmus test is first attested 1957, from scientific use of litmus-treated paper as a chemical indicator. Litmus paper with this meaning is from 1803.

litmus in Medicine

litmus lit·mus (lĭt'məs)
n.
A water-soluble blue powder derived from lichens that changes to red with increasing acidity and to blue with increasing basicity.

litmus in Science
litmus
  (lĭt'məs)   
A colored powder, obtained from certain lichens, that changes to red in an acid solution and to blue in an alkaline solution. Litmus is a mixture of various closely related heterocyclic organic compounds. ◇ Litmus is typically added to paper to make litmus paper, which can be used to determine whether a solution is basic or acidic by dipping a strip of the paper into the solution and seeing how the paper changes color.
litmus in Culture
litmus [(lit-muhs)]

In chemistry, a kind of paper used to tell whether a solution is an acid or a base. Acids turn blue litmus paper red; bases turn red litmus paper blue. Other testing paper or sophisticated instruments can be used to measure the pH of a solution more precisely.

Note: The term litmus is often used to refer to a general and simple test: “Your vote on this issue is a litmus test of your political philosophy.”