42 COMBINATIONS OF OXYGEN AND HYDROGEN. 



when it begins to boil, gas vviJI be evolved. Increase 

 the heat gradually, till the body and neck of the 

 retort become filled with a milky white vapour. In 

 this state, the temperature of the fused nitrate is 

 between 340 and 480°. After decomposition has 

 oroceeded for some minutes, so that the gas, when 

 examined, quickly enlarges the flame of a taper, it 

 may be collected over water. Care should be taken, 

 during the whole process, never to suffer the tem- 

 perature of the fused nitrate to rise above 500^ of 

 Fahrenheit; which may be easily judged of from 

 the density of the vapours in the retort, and from 

 the quick ebullition of the fused nitrate ; for if the 

 heat be increased beyond this point, the vapours in 

 the retort acquire a reddish and more transparent 

 appearance, and the fused nitrate begins to rise, 

 and occupy twice the bulk it did before. The 

 nitrous oxide, after its generation, should stand 

 over water for several hours; it is then fit for 

 respiration or other experiments. 



The explanation of this process is as follows: 

 Nitrate of ammonia consists of nitric acid and 

 ammonia ; nitric acid is composed of nitrous gas 

 and oxygen ; and ammonia consists of hydrogen 

 and nitrogen. At a temperature of 480°, the 

 attractions of hydrogen for the nitrogen in the 

 ammonia, and that of nitrous gas for the oxygen 

 of the nitric acid, are diminished; while, on the 

 contrary, the attractions of the hydrogen of the 

 ammonia for the oxygen of the nitric acid, and 

 that of the remaining nitrogen of the ammo- 

 nia for the nitrous gas of the nitric acid, are in- 

 creased; hence all the former affinities are broken, 

 and new ones produced; namely, the hydrogen of 

 the ammonia attracts the oxygen of the nitric acid, 

 the result of which is water. The nitrogen of the 



