NITROUS OXIDE. 



283 



NITROUS OXIDE. 



Syn. PROTOXIDE OF AZOTE, 

 1527-3; Qj. 



Eg. 277 or 22.2 ; NO ; density 



This gas was discovered by Dr. Priestley about 1776, and 

 studied by Davy, whose " Researches, Chemical and Philoso- 

 phical," published in 1809, contain an elaborate investigation of 

 its properties and composition. Davy first observed the stimu- 

 lating power of nitrous oxide when taken into the lungs, a 

 property which has since attracted a considerable degree of 

 popular attention to this gas. 



Preparation. Nitrous oxide is always prepared from the 

 nitrate of ammonia. Some attention must be paid to the purity 

 of that salt, which should contain no hydrochlorate of ammonia. 

 It is formed by adding pounded carbonate of ammonia to pure 

 nitric acid, which, if concentrated, may be previously diluted 

 with half its bulk of \vater, so long as there is effervescence ; 

 and a small excess of the carbonate may be left at the end in 

 the liquor. The solution is concentrated till its boiling point 

 begins to rise above 250, and a drop of it becomes solid on a 

 cool glass plate. On cooling, it forms a solid cake, which may 

 be broken into fragments. To obtain nitrous oxide, a quantity 

 of this salt, which should never be less than 6 or 8 ounces, is 

 introduced into a retort, or a globular flask, called a bolt-head 



a, and heated by a charcoal 

 choffer b, the diffused heat of 

 w r hich is more suitable than 

 the heat of a lamp. Paper 

 may be pasted over the cork 

 of the bolt-head to keep it 

 air-tight. At a temperature 

 not under 34 O a the salt boils 

 and begins to undergo decom- 

 position, being resolved into 

 nitrous oxide and water. As 

 heat is evolved in this decomposition, which is a kind of 

 combustion or deflagration, the choffer must be withdrawn 

 to such a distance from the flask, as to sustain only a mo- 

 derate ebullition. If the temperature is allowed to rise too 

 high, the ebullition becomes tumultuous, and the flask is 



FIG. 35. 



