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.
Alkaline diet
Nutrition scientists began to refine this hypothesis in the early 20th century, emphasizing the role of negatively charged particles (anions) and positively charged particles (cations) in food. Diets high in chloride, phosphate and sulfate (all of which are anions) were presumed to be acid forming, while diets high in potassium, calcium and magnesium (all of which are cations) were presumed to be alkaline forming. Other investigations showed specific foods, such as cranberries, prunes and plums had unusual effects on urine pH. While these foods provided an alkaline ash in the laboratory, they contain a weak organic acid, hippuric acid, which caused the urine to become more acidic instead.