- 12 NITROGEN. 



jar a portion of air. Into this air is to be brought a 

 piece of ignited phosphorus, contained in a little cup 

 so as to float on the surface of the water. Phosphorus, 

 as is well known, is very inflammable. While burn- 

 ing, it unites with the oxygen of the air, and forms 

 an important white acid compound called phosphoric 

 acid : to this we shall have occasion to refer again. 

 When the burning phosphorus is brought under the 

 jar, the above described process at once commences, 

 and continues till all of the oxygen in the air within 

 the jar has combined with phosphorus. The nitrogen 

 is now left nearly pure. A portion of the confined air 

 expanded by heat, of course escapes at first, and the 

 jar is filled with white fumes of phosphoric acid. 

 These are gradually absorbed by the water, until at 

 last the interior of the jar is quite clear. 



1. It is then to be perceived that this gas, like the 

 two preceding ones, is colorless, inodorous, and taste- 

 less. It has so few marked qualities that it is much 

 more easily distinguished from the others by saying 

 what it is not, than what it is. Among its negatives, 

 then, we find, 



2. That it does not support combustion : a lighted 

 taper, plunged into it, is extinguished instantly 



3. It does not burn itself, but remains unaltered 

 after contact with flame. 



4. It is a little lighter than atmospheric air. It will 

 for this reason remain some time in a jar held with 

 the mouth downward, but at once escapes if the jar be 

 inverted. Both of these facts may be shown by a 

 lighted taper. 



5. It will not support vegetation alone, and animals 

 soon die when placed in it. They do not seem to suffer 

 from any active poisonous influence, but from a species 

 of suffocation as in water. 



This gas is admirably adapted to the purpose which 

 it serves in the atmosphere, of tempering the too great 



