Crossword Genius

Dye material from lichens, used in acidity tests (6)

Ross

I believe the answer is:

litmus

(Other definitions for litmus that I've seen before include "Substance used to distinguish between acid and alkali" , "A dye used as a rough indicator of acid" , "dye encountered in testing" , "Substance used in test for acidity" , "Substance turned red by acids" .)

I've seen this clue in The Guardian.
Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.