Emily Dickinson Lexicon

POT'ASH, n. [pot and ashes; D. potasch; G. pottasche; Dan. potaske; Fr. potasse.]

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. – Kirwan. Nicholson. Encyc. By the discoveries of Sir H. Davy, it appears that the essential part of potash is a metallic oxyd; the metal is called potassium, and the alkali, in books of science, is called potassa.