Low-pH liquids (5)
I believe the answer is:
acids
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">low-ph liquids</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for acids that I've seen before include "Corrosive substances" , "they're sharp" , "They turn litmus paper red" , "They have a sour taste" , "They react" .)