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n. A water-soluble blue powder derived from certain lichens that changes to red with increasing acidity and to blue with increasing basicity.

n. A dyestuff extracted from certain lichens, that changes color when exposed to pH levels greater than or less than certain critical levels.

n. A simple test of acidity in a liquid using litmus, usually in the form of litmus paper.

n. A simple test of any attribute; a litmus test.

n. 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.

n. A peculiar coloring matter procured from Roccella tinctoria and some other lichens.

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

"‡ 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."

acid-base indicator   

litmus on rags    litmus paper   

litmus test    litmus paper   

lacmus   

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