Related Clues:

• Procaine predecessor
• Airwaves
• Composition of outer space, in old belief
• Old hospital administration
• Number
• Thin air
• Anesthesia of old
• Knock-out gas, once
• Old sleep inducer
• Upper regions
• Old-style anesthetic
• Old number
• Discovery of a Spanish chemist in 1275
• Old-fashioned anesthetic
• Volatile liquid