Related Clues:

• Heartburn cause
• Base antagonist?
• Beyond sarcastic
• See 43 Across
• 1960s hallucinogen
• Cause of a hippie high
• "Dropped" substance
• Leary's turn-on
• Blotter paper substance
• Part of RNA
• Sulphuric or nitric
• Boric, e.g.
• Low-pH substance
• '60s trip starter, initially
• Sour-tasting substance