AZOTIC GAS. 



tonates on the slightest motion ; often, indeed, 

 spontaneously without any agitation whatever. 



But azote enters into a combination with hy- 

 drogen, of considerable interest in a chemical 

 point of view, a it constitutes ammonia, or vola- 

 tile alkali, so much employed in chemical analy- 

 ses, and so often formed during the decomposi- 

 tion and putrefaction of animal substances. 



Ammonia Ammonia, in a state of purity, is a gaseous sub- 

 stance, easily obtained by heating a mixture of 

 sal-ammoniac and quicklime. 3i parts of pure 

 quicklime are sufficient to decompose 6| parts of 

 sal-ammoniac ; but it is better to add a consider- 

 able excess of quicklime. Indeed, I always fill 

 the small retort in which the sal-ammoniac is 

 put with quicklime, which is of service by pre- 

 venting the two speedy extrication of moisture, 

 which stops the evolution of the gas. 



Ammoniacal gas must be received over mer- 

 cury ; for it is the most absorbable of all the 

 gases by water, 1 volume of that liquid absorb- 

 ing 780 volumes of ammoniacal gas. 



Analysis of When pure dry ammoniacal gas in a glass 

 tube, standing over mercury, is exposed to a 

 continued series of electrical sparks passed 

 through it, decomposition takes place ; its volume 

 is just doubled ; and it is found to consist of a 

 mixture of one volume azotic and three volumes 

 hydrogen gas. This experiment was first made 

 by M. Berthollet senior. It was afterwards re- 



