62 CHEMISTRY. 



be readily obtained from common air in the mode represent- 

 ed in Fig. 11. Let a cork, with a 

 cup-shaped piece of chalk on it for 

 the reception of a bit of phosphorus, 

 float in a pneumatic trough, d. Aft- 

 er igniting the phosphorus, hold over 

 it a glass jar, a, keeping the edge of 

 its mouth immersed in the water. 

 After a little time there is nothing 

 Fig. 11. - n tne j ar k u fc nitrogen gas nearly 



pure. The explanation is this : As the phosphorus burns, it 

 unites with the oxygen of the air in the jar, thus making 

 phosphoric anhydride, as phosphorus burned in pure oxy- 

 gen does ( 58). This rises in fumes, and is mingled with 

 the nitrogen. We have then nitrogen "and phosphoric an- 

 hydride in the jar. How do we get the nitrogen separate ? 

 Wait a little, and the fumes disappear, for the phosphoric 

 anhydride dissolves readily in the water in the pneumatic 

 trough, leaving the nitrogen alone in the jar. The nitrogen 

 occupies less space by one fifth than the air in the jar did, 

 for the oxygen that has disappeared was one-fifth part of 

 the air. The cork, therefore, rises somewhat in the jar during 

 the process, being pushed up by the water to take the place 

 of the oxygen. The water now contains phosphoric acid. 



67. Properties of Nitrogen. Nitrogen is lighter than air, 

 its specific gravity being .972. Like oxygen, it is transpar- 

 ent, without color, taste, or smell. But it is very different 

 from oxygen in some of its properties. Nothing will burn 

 in it. The contrast between the two gases in this respect 

 can be very prettily shown if you have two jars filled with 

 them. If you let a lighted taper down into the jar of ni- 

 trogen, it will go out. If now you introduce it quickly into 

 the jar of oxygen, it will light up again and burn brilliant- 

 ly ; and you can pass it back and forth from one jar to the 



