252 SMITH'S INTERMEDIATE CHEMISTRY 



the former diminishing and the latter increasing in number as the 

 temperature is raised. 



All the metals, excepting gold and platinum, combine with suU 

 phurjtn form.-sulphides, and in most cases much heat is given out 

 during the union. Sulphur unites with chlorine to give sulphur 

 monochloride S 2 Cl2, used in vulcanizing rubber, and burns in 

 oxygen to give sulphur dioxide :* 



S + 2 -S0 2 . 



In these compounds the valence of an atomic weight of sulphur 

 appears to be one (in S 2 Cl2) or four (in S0 2 ). These are excep- 

 tional values, however, the common valences being two (in H 2 S, 

 ZnS, etc.) and six (in S0 3 , S0 2 C1 2 , etc.). 



Moist sulphur is slowly oxidized at ordinary temperatures to 

 sulphuric acid: 



Skeleton: S + H 2 + O 2 -+H 2 SO 4 . 



Balanced: 2S + 2H 2 O + 3O 2 -> 2H 2 S0 4 . 



In the equations, the simple formula S is used in place of a 

 molecular formula. The latter is needed only when questions 

 about the volume of the vapor are asked, and sulphur is almost 

 always used only in solid or melted form. Then, too, the vapor 

 contains several kinds of molecules, and using Ss or SG would 

 introduce large and inconvenient coefficients. 



HYDROGEN SULPHIDE H 2 S 



Occurrence. Sulphur is a constituent of albumen, of which, 

 for example, the white of an egg is composed. When decay takes 

 place within the shell, so that air is excluded and the oxidation 

 which accompanies ordinary decay is prevented, the sulphur gives 

 hydrogen sulphide. The latter can be recognized by its odor. 

 Some mineral waters contain a small amount in solution. 



* Traces of sulphur trioxide are found at the same time. They give minute 

 drops of sulphuric acid, which cause a haziness in the gas when it is formed 

 by this action. 



