litmus
/ˈlɪtməs/ noun C2- A dyestuff extracted from certain lichens, that changes color when exposed to pH levels greater than or less than certain critical levels.
- A simple test of acidity in a liquid using litmus, usually in the form of litmus paper.
- A simple test of any attribute; a litmus test.
Plural litmuses
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In his right hand he held a slip of litmus-paper.
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