the world > the earth > minerals > types of mineral > nitrates > [adjective] > potassium nitrate (4)
of the nature of saltpetre.
pertaining to, of the nature of, or impregnated with, saltpetre.
Of, containing, or derived from nitre or nitric acid; of or containing nitrogen, esp. in a relatively high oxidation state (often 5). Cf. nitric acid…