192 



METALLOIDS. 



The carbonic acid immediately escapes with renewed 

 and rapid effervescence. 



471. FLAME EXTINGUISHED 



What effect 



lias carbonic BY CARBONIC ACID. - Lower a 



acid onflame? lighted taperj can dl e , or splinter 

 of wood into a vial of carbonic acid, pre- 

 pared as before directed. The flame will 

 be immediately extinguished, as if it had 

 been dipped in water. 



Give another ^^' * ^ Sam<3 6X P ermient mav 



method of per- performed by pouring the 



M as into a vial - at the bot - 



torn of which is a bit of 



lighted candle. Nothing will be seen 



to flow from one vessel into the other, 



but the effect will be the same as before. 



473. CARBONIC ACID is 



Of what use 



to plants is FOOD FOR PLANTS. Carbonic 



carbonic acid? ^^ ig Qne Q the principal 



elements of the food of plants. The leaves absorb 

 it from the air, and the roots from the earth, and 

 convert it into wood and fruit. The subject is fur- 

 ther considered in the latter part of this work. 



474. IT is POISON FOR ANIMALS. Wa- 

 ter impregnated with carbonic acid is a 

 healthful drink ; but the same gas, when 

 taken into the lungs, produces death. It 

 operates negatively, by excluding the air, and also 

 positively, as a poison. Being heavier than the air, 

 lakes of this gas sometimes collect in the bottom of 

 caverns. There is a grotto of this kind in Italy, called 



What is the 



effect of car- 

 b 



