What is "nitrary"

n. A place where potassium nitrate or saltpetre is produced.

A ' nitrary' is a place of production of potassium nitrate or saltpetre used primarily for the manufacture of gunpowder. The saltpetre occurs naturally in certain places like the "Caves of Salnitre" (Collbató) known since the Neolithic –Cova del rat penat– the guano (bat excrements) deposited over thousands of years became saltpetre after being leached by the action of meteoric water.