230 ALKALIES. 



gress towards obtaining the pure alkali. The muriatic acid is also a 

 gaseous body : it cannot be expelled from the alkalies by heat : it can 

 be displaced by the sulphuric acid, but that will only engage the alkali 

 in a new combination : to remove it entirely, we employ lime in this 

 case also, which will attract it away and leave the alkali free and pure.* 



AMMONIA POTASSA SODA LITHIA. 



GENERAL CHARACTER OF ALKALIES. 



!a.} Caustic to the animal organs. 

 6.) Volatilizable by heat, but, except ammonia, not decomposable 

 by heat alone. 



(c.) Combine with acids and form salts $f acids and alkalies are 

 antagonists. 



(d.) Very soluble in water, even in the state of carbonate ; solu- 

 ble also in alcohol. 



(e.) Turnf most blue, purple, and other dark vegetable colors, to 

 green ; as tincture or infusion of violets, and of purple cabbage. 



(f.) Turn most yellow vegetable colors to brown ; as turmeric and 

 rhubarb ; and red to purple, as tincture of brazil wood. 



(g.) The colors altered by an alkali, are generally restored by a 

 due proportion of an acid. 



(h.) Unite with oils and form soaps ; corrode woollen cloth ; and 

 are generally powerful solvents of animal matter. 



(i.) Taste, acrid and peculiar; particularly different from that pro- 

 duced by acids ; it is called the alkaline taste, and in a milder form, 

 is observed in pearl ashes and soda. 



SEC. I. AMMONIA. || 



Remark. This alkali is placed first because of its relation to ni- 

 trogen, and hydrogen, which have been described. 



* Had we begun with acids, an explanatory statement would have been necessary 

 respecting alkalies and salts, as two of the most important of the acids, the nitric and 

 muriatic, are extracted from saline combinations. 



t The definition of alkali proposed by Dr. Ure, founded on the power of " com- 

 bining with acids, so as to neutralize or impair their activity," would confound them 

 with the earths and metallic oxides. 



t The power to affect vegetable colors, continues even after combination with 

 carbonic acid, which distinguishes the alkaline from the earthy carbonates. Ammo- 

 nia being a volatile alkali, sometimes escapes by evaporation, and the original color 

 is thus restored. 



Bibulous paper, wet with these colored solutions, forms test papers, by which 

 the application of colors is easily made. Litmus is not changed by alkalies, but if 

 previously reddened, it is turned back by an alkali to its original color, and thus be- 

 comes a test. 



|| Called also the volatile alkali. Popular name hartshorn, because it was an- 

 ciently distilled from the horns of the hart or deer, which, in common with other 

 animal matter contain its elements. 



