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HNO3, later called agenothree, was a liquid chemical that served multiple purposes on Pern.
Agenothree's most popular use was as an agent against Thread. Paul Benden noted that it was as effective as using fire and water to kill Thread. Agenothree tanks were used by riders of Queen dragons, as the queens could not chew firestone. Riders flew low to catch Thread missed by the fighting wins. Agenothree was also used by ground crews to eliminate burrows. By the Ninth Pass, however, knowledge of agenothree's use as a Thread antagonist appeared to have decreased. While attempting to redevelop flamethrowers, Fandarel developed a pump that sprayed Agenothree to eliminate burrows.
In addition to its use against Thread, agenothree was also used by the Smithcraft and Farmercraft. Agenothree was used by the Smithcraft as an aid in etching metal. Meanwhile, the Farmercraft used diluted agenothree as a fertilizer for plants.