One side of a chemistry scale (5)

I believe the answer is:

acids

(Other definitions for acids that I've seen before include "they're sharp" , "Corrosive substances" , "They turn litmus paper red" , "They have a sour taste" , "They react" .)

I've seen this clue in The New York Times.

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.