- potassium carbonate (esp. when obtained from wood ashes)
- potassium hydroxide
- any substance containing potassium; esp., salts derived from natural brines, distillery waste, flue dusts of blast furnaces, etc., whose potassium content is expressed in terms of KO: used in fertilizers, soaps, etc.
Origin of potashearlier in plural , potashes from Dutch potasschen from pot, pot + asch, ash: origin, originally prepared by evaporating the lixivium of wood ashes in iron pots