Alkali
In chemistry, an alkali (; from Arabic: "al-qaly" "ashes of the saltwort") is a basic, ionic salt of an alkali metal or alkaline earth metal chemical element. An alkali also can be defined as a base that dissolves in water. A solution of a soluble base has a pH greater than 7.0. The adjective alkaline is commonly, and alkalescent less often, used in English as a synonym for basic, especially for bases soluble in water. This broad use of the term is likely to have come about because alkalis were the first bases known to obey the Arrhenius definition of a base, and they are still among the most common bases.
Leblanc process
Soda ash (sodium carbonate) and potash (potassium carbonate), collectively termed "alkali", are vital chemicals in the glass, textile, soap, and paper industries. The traditional source of alkali in western Europe had been potash obtained from wood ashes. However, by the 13th century, deforestation had rendered this means of production uneconomical, and alkali had to be imported. Potash was imported from North America, Scandinavia, and Russia, where large forests still stood. Soda ash was imported from Spain and the Canary Islands, where it was produced from the ashes of glasswort plants (called barilla ashes in Spain), or imported from Syria. The soda ash from glasswort plant ashes was mainly a mixture of sodium carbonate and potassium carbonate. In addition in Egypt, naturally occurring sodium carbonate, the mineral natron, was mined from dry lakebeds. In Britain, the only local source of alkali was from kelp, which washed ashore in Scotland and Ireland.