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ALKALI

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Originally appearing in Volume V01, Page 674 of the 1911 Encyclopedia Britannica.
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ALKALI , an Arabic See also:

term originally applied to the ashes of See also:plants, from which by lixiviation carbonate of soda was obtained in the See also:case of See also:sea-plants and carbonate of potash in that of See also:land-plants. The method of making these " mild " alkalis into " See also:caustic " alkalis by treatment with See also:lime was practised in the See also:time of See also:Pliny in connexion with the manufacture of See also:soap, and it was also known that the ashes of See also:shore-plants yielded a hard soap and those of land-plants a soft one. But the two substances were generally confounded as " fixed alkali " (carbonate of See also:ammonia being " volatile alkali "), till See also:Duhamel du Monceau in 1736 established the fact that See also:common See also:salt and the ashes of sea-plants contain the same See also:base as is found in natural deposits of soda salts (" See also:mineral alkali "), and that this See also:body is different from the " See also:vegetable alkali " obtained by incinerating land-plants or See also:wood (pot-ashes). Later, See also:Martin Heinrich See also:Klaproth, finding vegetable alkali in certain minerals, such as See also:leucite, proposed to distinguish it as potash, and .at the same time assigned to the mineral alkali the name natron, which survives in the See also:symbol, Na, now used for See also:sodium. The word alkali supplied the symbol for See also:potassium, K (kalium). In See also:modern See also:chemistry alkali is a See also:general term used for compounds which have the See also:property of neutralizing acids, and is applied more particularly to the highly soluble hydrates of sodium and potassium and of the three rarer "alkali metals," See also:caesium, See also:rubidium and See also:lithium, also to aqueous ammonia. In a smaller degree these alkaline properties are shared by the less soluble hydrates of the "metals of the alkaline earths," See also:calcium, See also:barium and See also:strontium, and by See also:thallium See also:hydrate. An alkali is distinguished from an See also:acid or neutral substance by its See also:action on See also:litmus, See also:turmeric and other indicators.

End of Article: ALKALI

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