Related Clues:

• Kind of rock or rain
• Tart-tasting
• Aspirin, e.g.
• Citric ___
• Test subject
• Word with indigestion or test
• Irritability
• Trypsin, e.g.
• Caustic comments
• Sour-tasting
• Battery fill
• Hydrochloric, for one
• Heartburn remedy
• It may settle things
• Litmus-reddening substance