EIGHTEENTH CENTURY. 



PT. in; 



bottle, a, Fig. 40, and poured upon them some water and 

 some acid He then stopped the bottle with a tight cork, 

 and joined it by the tube b to a large glass jar, c, filled with 

 water, and standing with its open end downwards in a 

 vessel of water. Immediately bubbles began to rise from 



FIG. 40. 



Carbonic Acid rising from Limestone and Acidulated Water (Griffin); 



a, Bottle containing pieces of limestone in water and acid, b, Connecting tube. 



c, Inverted jar, out of which the rising gas is driving the water. 



the limestone, and passing into the jar, t, drove out the 

 water and filled the jar with gas. 



This gas Black called * fixed air,' because it had been 

 fixed in the limestone before it was driven out by the 

 acid. He collected and weighed it, and found that it exactly 

 made up the weight which the limestone had lost. He then 

 reversed the experiment, and taking some water, which had 

 lime dissolved in it, he passed some ' fixed air ' into it, and, 

 as he expected, the gas joined itself to the lime and formed 

 a powdered white chalk at the bottom of the bottle. By 

 these two experiments he proved that limestone and chalk 

 are composed of lime and 'fixed air,' and that lime can be 

 turned into chalk by causing fixed air to combine with it. 



He then proceeded to examine the gas itself. He found 

 that animals died in it, and that a flame would not burn in 



