74 CARBON AND NITROGEN. 



with a blue lambent flame, but does not explode 

 when mixed with atmospheric air. It is pro- 

 cured by depriving carbonic acid of part of its 

 oxygen. This is effected by exposing equal parts 

 of chalk and filings of zinc to a gradual red heat, 

 suftering the first product to escape, which is car- 

 bonic acid gas. The zinc deprives the carbonic 

 acid in the chalk of part of its oxygen. 



Carbon and Nitrogen. 



This combination is called cyanogen. It is a gas- 

 eous body, having a penetrating and peculiar 

 smell, and burning with a purple flame. It red- 

 dens vegetable blues. 



When cyanogen combines with hydrogen, it 

 forms a triple compound, called hydrocyanic acid : 

 this is also called Prussic acid. Prussic acid is a 

 liquid having a very pungent odour, like that of 

 bitter almonds. It is extremely acrid, and highly 

 poisonous. It is called Prussic acid, because it 

 forms one of the constituents of the well-known 

 pigment Prussian blue, which is a combination of 

 hydrocyanate of iron with alumine. 



PHOSPHORUS. 



This highly inflammable substance is not met 

 with in nature uncombined ; but it exists combined 

 with oxygen, forming phosphoric acid, in many 

 animal and mineral substances. 



Phosphorus is a yellowish semi-transparent mat- 

 ter of the consistence of wax. It is luminous in 



