Related Clues:

• Dropped drug
• Low-pH
• Etching aid
• Litmus-paper reactant
• Vicious
• Battery contents
• With 44-Across, polluted precipitation
• Word with rock, rain or test
• Caustic liquid
• Limelike
• Ill-natured
• Trip agent?
• One litmus test conclusion
• Caustic compound
• Hydrofluoric ___