Scientific test on two of the humanities? (6)
I believe the answer is:
litmus
But I can't explain it at all! Could you help me understand?
(Other definitions for litmus that I've seen before include "Paper used to test for acid or alkali" , "Substance used to distinguish between acid and alkali" , "It turns red with acids and blue with alkalies" , "paper for chemistry test" , "Acid-alkali testing substance" .)