litmus

American  

[lit-muhs] / 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.

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litmus British  

/ 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

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litmus Scientific  

/ lĭt′məs /

1. 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.

2. ◆ 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.

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litmus Cultural  

1. 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.

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Discover More

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.”

Etymology

Origin of litmus

1495–1505; earlier lytmos < Old Norse litmosi dye-moss, equivalent to lit- color, dye + mosi moss

Explanation

Litmus is a special dye that's used to determine how acidic a substance is. Scientists use litmus to test liquids or gases to see if they're an acid or a base. Litmus is the mix of dyes that's used to make litmus paper, a scientific tool that makes it easy to see if a material has an acidic pH. Made from lichen, litmus can be absorbed onto paper which turns blue to indicate an alkaline substance and red if it's acidic. Litmus comes from the Middle Dutch word lijkmoes, which combines lac, "red resinous substance" and moes, "pulp."

Example Sentences

Three days later, Litmus Test faded to third place in his first start of the year, the Rebel Stakes at Oaklawn Park in Arkansas.

From Los Angeles Times • Mar. 6, 2026

Singer Katy Perry has signed a deal to sell rights to five of her studio albums released between 2008 and 2020 including "Teenage Dream" to Carlyle-backed Litmus Music, the music rights company said on Monday.

From Reuters • Sep. 26, 2023

The sale was made to Litmus Music, a music rights management company financially backed by the Carlyle Group private equity firm.

From Washington Times • Sep. 19, 2023

Litmus now owns Perry's stake in the master recordings and publishing for the records, meaning it will collect any future royalties the music earns.

From BBC • Sep. 19, 2023

Litmus can be employed successfully with the strong acids and bases, and also with ammonium hydroxide, although the salts of the latter influence the indicator unfavorably if present in considerable concentration.

From An Introductory Course of Quantitative Chemical Analysis With Explanatory Notes by Talbot, Henry P.