SODA-WATER. 



bubble of air shall be at the top when the bottle lies down, 

 so, the air will eventually escape, no matter how tightly 

 the cork be put in. The ordinary " soda-water " con- 

 tains scarcely any soda. It is merely water, chalk,(?J 

 and carbonic acid. The " Gazogene " is made useful 

 for small quantities of soda-water, and is arranged 

 in the following manner. The appearance of it is 

 familiar to all. It consists of a double vessel, into 

 the upper part of which a solution of any kind wine 

 and water, or even plain water is put, to be saturated 

 with carbonic acid, or "aerated," and into the lower 

 one some carbonate of soda and tartaric acid. A 

 tube leads from this lower to the top of the upper 

 vessel, which screws on and off. By shaking the 

 apparatus when thus charged and screwed together, 

 some of the liquid descends through the tube into 



373 

 If it be not kept 



Fig. 370. Gazogene. 



Fig. 371. Soda-water apparatus. 



the lower vessel and moistens the soda and acid, which therefore act on 

 each other, and cause carbonic acid to be disengaged ; this, rising up 

 through the tube (which is perforated with small holes at the upper part), 

 disperses itself through the liquid in small bubbles, and causes sufficient 

 pressure to enable the liquid to absorb it, which therefore effervesces when 

 drawn off by the tap. 



Carbonic acid can be liquified, and then it is colourless. In a solid 

 form it resembles snow, and if pressed with the fingers it will blister them. 

 Being very heavy the gas can be poured into a vase, and if there be a 

 light in the receptacle the flame will be immediately extinguished. 



That even the gas introduced into seltzer-water is capable of destroy- 

 ing life, the following experiment will prove. Let us place a bird within a 



