Saltpetre

Saltpeter is another name for the mineral form of potassium nitrate. Filings and rasplings of it are used as an ingredient in Polyjuice Potion. It was kept with other potion ingredients in the Potions Classroom at Hogwarts School of Witchcraft and Wizardry.

Appearances

 * Harry Potter and the Chamber of Secrets (film)
 * The Road to Hogwarts Sweepstakes