litmus
UK: ˈlɪtməs | US: ˈlɪtməs
n. A water-soluble mixture of dyes extracted from lichens, used as a pH indicator (turns red in acid, blue in alkali).
The word "litmus" likely originates from Old Norse litmosi, combining litr (meaning "color" or "dye") and mosi (meaning "moss"). This reflects its source—lichen-derived dyes used for testing acidity. Over time, the term evolved in Middle Dutch (lēcmoes) and later English to specifically denote the pH-sensitive compound. The "moss" connection highlights its natural origin, while "color" underscores its function as a visual indicator.
The scientist dipped litmus paper into the solution to test its pH.
Litmus turns red in acidic substances like lemon juice.
Blue litmus indicates a basic or alkaline environment.
Historically, litmus was extracted from lichens in Scandinavia.
The experiment required both red and blue litmus for verification.