POT'ASH, noun [pot and ashes.] The popular name of vegetable fixed alkali in an impure state, procured from the ashes of plants by lixiviation and evaporation. The matter remaining after evaporation is refined in a crucible or furnace, and the extractive substance burnt off or dissipated. Refined potash is called pearlash. The plants which yield the greatest quantity of potash are wormwood and fumitory.

By recent discoveries of Sir H. Davy, it appears that potash is a metallic oxyd; the metal is called potassium, and the alkali, in books of science, is called potassa.