 The word "barilla" was also used directly to refer to soda ash from any plant source, including not only the saltworts grown in Spain, but also glassworts, mangroves, and seaweed.These types of plant-derived soda ash are impure alkali substances that contain widely varying amounts of sodium carbonate (Na2CO3), some additional potassium carbonate (also an alkali), and a predominance of non-alkali impurities.The sodium carbonate, which is water-soluble, is "lixiviated" (extracted with water) from the ashes of the burned, dried plants.