litmus

litmus is defined in Webster's Unabridged Dictionary (1913) with 1 sense. The full text of each entry is reproduced verbatim below.

Definitions

1.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. Note: Litmus is used as a dye, and being turned red by acids and restored to its blue color by alkalies, is a common indicator or test for acidity and alkalinity. Litmus paper (Chem.), unsized paper saturated with blue or red litmus, -- used in testing for acids or alkalies.

Source: Webster's Unabridged Dictionary, 1913 edition (public domain, via GCIDE / Project Gutenberg).

Definitions: Webster's Unabridged Dictionary, 1913 edition (public domain, via GCIDE / Project Gutenberg).
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