262 Chemistry [Lecture 33. 



Let the water be taken at the spring-head, 

 and put into a quart bottle, over which a bladder 

 is to be tied, or, what is better, in the mouth 

 of the bladder one end of a tube must be insert- 

 ed, and the other end fixed in the cork of the 

 bottle, so as to be even with the bottom of the 

 cork; through this tube the air is to be con- 

 veyed ; the bottle is then to be immersed in a ves- 

 sel containing water, which is gradually made to 

 boil, but not so as to boil the mineral water. 

 By this heat the air will be expelled out of the 

 water into the bladder ; the bladder is then to be 

 immersed in cold water in a graduated vessel ; 

 into this water the air of the bladder must be 

 squeezed. By the degree to which the water 

 rises we may determine the quantity in bulk 

 that the air amounts to. But if we would know 

 whether this air is common air or carbonic, we 

 must repeat the experiment with another bottle, 

 and apply the tube to a caustic alkaline lye; the 

 tube must then have a funnel fixed to its end, 

 that the air may be applied more extensively to 

 the lye, and be sooner absorbed by it ; in a short 

 time all the carbonic acid gas will be absorbed, 

 and the caustic lye will leave only the common 

 air. This effect is easily explained on the prin- 

 ciples which you have already learned. Every 

 alkali in its pure state is caustic. It is neu- 

 tralized by the accession of carbonic acid, for 

 which it has a great attraction. The lye is only 

 the alkali dissolved in water. Thus we may 



