AIR AND OXYGEN 35 



Specific Chemical Properties of Oxygen. The chemical 

 properties of pure oxygen are like those of atmospheric air, only 

 more pronounced. 



Reactions with Non-metallic Elements. Sulphur, when raised in 

 advance to the temperature necessary to start the action, unites 

 vigorously with oxygen, giving out much heat and producing a 

 familiar gas having a pungent odor (sulphur dioxide). This 

 odor is frequently spoken of as the " smell of sulphur," but in 

 reality sulphur itself has no odor, and neither has oxygen. The 

 odor is a property of the compound of the two. The mode of 

 experimentation can be changed and the oxygen led into sulphur 

 vapor through a tube. The oxygen then appears to burn with 

 a bright flame, giving the same product as before. 



Phosphorus, when set on fire, blazes in oxygen very vigorously, 

 forming a white, powdery, solid oxide phosphorus pentoxide. 

 Burning carbon, in the form of charcoal or hard coal, glows bril- 

 liantly and is soon burnt up. It leaves an invisible, odorless gas 

 carbon dioxide. At high temperatures, oxygen combines 

 readily with one or two other non-metals (e.g., silicon, boron, and 

 arsenic), and to a small extent (1 per cent at 1900) with nitrogen. 

 It will not combine directly with chlorine, bromine, or iodine, 

 although oxides of the first and last can be prepared by using 

 other varieties of chemical change. With the six members of the 

 helium family of which no compounds are known, and with 

 fluorine, oxygen forms no compounds. 



Sulphur (32.06)+ Oxygen (32)->Sulphur dioxide (64.06). 

 Phosphorus (62. 08)+ Oxygen (80) -^Phosphorus pentoxide (142.08). 

 Carbon (12)+0xygen (32)-^Carbon dioxide (44). 



Reactions with Metallic Elements. Iron, as we have seen, rusts 

 exceedingly slowly in air and, even when red-hot, gives hammer- 

 scale, the black solid which is broken off on the anvil, rather 

 deliberately. In pure oxygen, a bundle of picture-wire, if once 

 ignited, will burn with surprising brilliancy, throwing off sparkling 



