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.
Alkali metal nitrate
Alkali metal nitrates are chemical compounds consisting of an alkali metal (lithium, sodium, potassium, rubidium and caesium) and the nitrate ion. Only two are of major commercial value, the sodium and potassium salts. They are white, water-soluble salts with relatively similar melting points.
The main uses of alkali metal nitrates are in fertilizers in the case of the sodium and potassium derivatives. They are also commonly used in explosives and pyrotechnic compositions; they are strong oxidizers. Other uses are for coloring in fireworks: caesium nitrate produces an indigo color, potassium nitrate and rubidium nitrate produce violet colors, lithium nitrate produces a red color, and sodium nitrate produces a yellow color.