40 



COMBINATIONS OF OXYGEN AND NITROGEN. 



Nitrogen and oxygen unite together in four 

 different proportions : 



1. Nitrous oxide, in which the oxygen is but 

 half the vokime of the nitrogen. 



2. Nitric oxide, in which the volumes of oxygen 

 and nitrogen are equal. 



3. Nitrous acid, in which the volume of oxygen 

 is twice the volume of nitrogen. 



4. Nitric acid, in which the oxygen is two and a 

 half times the volume of nitrogen. 



Nitrons oxide. This gaseous compound, called 

 also the gaseous odide of nitrogen, or the gaseous 

 oxide of azote, was first discovered by Dr. Priestley ; 

 but it is to Sir Humphry Davy that we owe a 

 tliorough knowledge of its properties. 



Nitrous oxide is a permanent gas. A candle burns 

 in it with a brilliant flame and crackling noise ; be- 

 fore its extinction, the white inner flame becomes 

 surrounded with a blue one. Phosphorus intro- 

 duced into it, in a state of inflammation, burns with 

 increased splendour, as in oxygen gas. 



Sulphur, introduced into it when burning with a 

 feeble blue flame, is extinguished ; but when in a 

 state of vivid inflammation, it burns with a rose- 

 coloured flame. Lighted charcoal burns in it more 

 brilliantly than in atmospheric air. 



Iron wire, v/ith a small piece of wood affixed to 

 it, and introduced inflamed into a vessel filled with 

 this gas, burns rapidly, and throws out bright scin- 

 tillating sparks. 



Nitrous oxide is rapidly absorbed by water that 

 has been boiled, and a quantity of gas equal to rather 

 more than half the bulk of the water may be thus 



