in Chemistry, denotes a particular class of salts. The word alkali is of Arabian origin, and was introduced into chemistry after it had been applied to a plant which still retains the name of kali. When this plant is burnt, the ashes walked in water, and the water evaporated to dryness, a white substance remains, which was called alkali. According to Albertus Magnus, who uses the word, it signifies fæx amaritudinis, "the dregs of bitterness." Alkali may be obtained from other substances besides kali. Chemists gradually discovered that bodies, differing from one another in several of their properties, had been confounded together under the same name. The word, in consequence, became general, and is now applied to all bodies which possess the following properties: 1. Incombustible. 2. A hot caustic taste. 3. Volatilized by heat. 4. Soluble in water even when combined with carbonic acid. 5. Capable of converting vegetable blues to green.

The alkalis at present known are three in number: 1. Potash; 2. Soda; 3. Ammonia. The two first are called fixed alkalis, because they require a red heat to volatilize them; the last is called volatile alkali, because it readily assumes a gaseous form, and consequently is dissipated by a very moderate degree of heat. See Chemistry Index.

or Sal Kali. See Salicornia, Botany Index.