ETYM Dutch lakmoes; lak lacker + moes a thick preparation of fruit, pap, prob. akin to Eng. meat: cf. German lackmus. Related to Lac a resinous substance.
Dye obtained from lichens, used in chemical tests, being turned red by acid and blue by alkali.
A coloring material that turns red in acid solutions and blue in alkaline solutions; used as an acid-base indicator.
Dye obtained from various lichens and used in chemistry as an indicator to test the acidic or alkaline nature of aqueous solutions; it turns red in the presence of acid, and blue in the presence of alkali.