36 OXYGEN — NITROGEN. 



bad air Nitrogen, or Azote: but we must not suppose 

 that, because the nitrogen appears thus useless, it is 

 really so ; for it is, in fact, of very great importance, 

 as we shall hereafter see. In the experiment just 

 mentioned, of burning the candle in a large bottle, 

 the oxygen is all combined with the elements of the 

 tallow, for which they have a strong affinity, whilst 

 the nitrogen is left unchanged because it cannot com- 

 bine with them ; for the same reason, also, it puts out 

 a fresh-lighted candle plunged into it. 



28. Oxygen, when obtained pure, and separate 

 from any other substance, is a gas like common air 

 in its ordinary characters, but remarkable for the 

 very brilliant manner in which all kinds of combus- 

 tible matter burn in it. Oxygen may be breathed 

 with safety, but it causes all the functions of the ani- 

 mal system to be carried on with great vigor and 

 rapidity, so much so, that an animal breathing pure 

 oxygen would be soon destroyed, from the very power- 

 ful effect which the gas would have on its organs. 

 Oxygen has a strong affinity for most of the other 

 elements, and combines with them to form a numerous 

 and important series of compounds. 



29. Nitrogen, though it resembles oxygen in ap- 

 pearance, yet differs from it very remarkably in 

 chemical characters; it extinguishes flame, and can- 

 not support the combustion of any substance ; it is 

 irrespirable, suffocating animals if they attempt to 

 breathe it pure, and seeming to have very little affi- 

 nity for other elements ; at least under ordinary tir- 



