CHEMISTRY 239 



reactions into which they may enter, while 

 their formation unquestionably does depend 

 upon the intervention of both hydrogen and 

 oxygen. All told, the chemical substances 

 which contain neither carbon, nor hydrogen, 

 nor oxygen make up only a few per cent of 

 known bodies. 



It is also clear that an especial^ large pro- 

 portion of the most active inorganic com- 

 pounds contain either hydrogen or oxygen. 

 All acids contain hydrogen; most of them 

 oxygen as well. All bases contain oxygen. 

 Moreover, the most important classes of re- 

 actions of inorganic chemistry are probably 

 oxidations and reductions, and the formation 

 of salts from acids and bases. In such pro- 

 cesses both oxygen and hydrogen are con- 

 cerned. 



In addition to the oxides and resulting 

 bases and acids, a few other important sub- 

 stances which contain hydrogen or oxygen 

 may be cited : ozone 3 , hydrogen peroxide 

 H 2 2 , ammonia NH 3 , hydrazine N 2 H 4 , hydrox- 

 ylamine NH 2 OH, sulphuretted hydrogen H 2 S, 

 hydrochloric acid HC1, nitrosyl chloride NOC1, 

 thionyl chloride SOCl 2 , phosgene COCl 2 , phos- 

 phine PH 3 , phosphorus oxy chloride POCl 3 , 

 arsine AsH 3 . Such compounds, and many 

 other similar ones, are of great importance on 



