Alkali

alkali (ăl`kəlī) [Arab., al-gili=ashes of saltwort], hydroxide of an alkali metal. Alkalies are readily soluble in water and form strongly basic solutions with a characteristic acrid taste. They neutralize acids, forming salts and water. Strong alkalies (e.g., those of sodium or potassium) are sometimes called caustic alkalies. The term alkali originally applied to salts obtained from plant ashes and is sometimes applied to a carbonate of sodium or potassium or to the hydroxide of an alkaline-earth metal.

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alkali

Inorganic compound, any soluble hydroxide (−OH) of the alkali metals: lithium, sodium, potassium, rubidium, and cesium. More broadly, ammonium hydroxide (see ammonia) and soluble hydroxides of the alkaline earth metals are also called alkalies. Strong bases that turn litmus paper blue, they react with acids to yield salts, are caustic, and in concentrated form corrode tissues. Sodium hydroxide (caustic soda) and potassium hydroxide (caustic potash) are very important industrial chemicals, used in the manufacture of soaps, glass, and many other products. The mineral trona, a compound of sodium carbonate and bicarbonate, is one naturally occurring alkali. It may be mined or recovered from dry lake beds.

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alkali

1. Chem a soluble base or a solution of a base

2. a soluble mineral salt that occurs in arid soils and some natural waters

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alkali [′al·kə‚lī]

(chemistry)

Any compound having highly basic qualities.

(petrology)

alkalic

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alkali

Any of the various chemically active bases such as the soluble salts of metals, e.g., the water-soluble salts of sodium and potassium which occur in constituents of concrete and mortar that may result in deleterious expansion.

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Alkali 

a base in aqueous solution. Aqueous alkaline solutions have high concentrations of OH^– (hydroxyl) ions. Alkalies include the hydroxides of the alkali metals, the alkaline-earth metals, and ammonium.

Most alkalies are highly hygroscopic white solid compounds. Their dissolution in water is accompanied by the liberation of large amounts of heat. Alkaline solutions change the color of acid-base indicators. The strongest, that is, caustic, alkalies are the hydroxides of the alkali metals, such as NaOH and KOH, while the weakest alkalies are ammonium hydroxide and the hydroxides of the alkaline-earth metals, such as Ca(OH)₂ and Ba(OH)₂. Also sometimes considered as alkalies are the salts of strong bases and weak acids (seeACIDS AND BASES), whose aqueous solutions exhibit alkaline reactions, for example, the hydro-sulfides NaSH and KSH, the carbonates Na₂CO₃ and K₂CO₃, the hydrocarbonate NaHCO₃ and the borax Na₂B₄O₇. Alkalies are commonly used in laboratory work and in industry (seeSODIUM HYDROXIDE; POTASSIUM HYDROXIDE; and CALCIUM HYDROXIDE).