THE CHEMISTRY OF WATER. HYDROGEN. 129 



ical; you will see that radicals play a very important part 

 in organic chemistry. 



165. How Cyanogen is Obtained. Though you can make carbon 

 and oxygen unite, forming carbonic anhydride, and oxygen and hydrogen, 

 forming water, you can not make carbon and nitrogen unite to form cyan- 

 ogen. This substance can be obtained only in an indirect manner. A 

 cyanide of some metal is first formed, and then the cyanogen is obtained 

 from this. We will state the process by which one of the cyanides, the cya- 

 nide of potassium, is formed. Potassium carbonate is strongly heated with 

 some refuse animal matter, as leather, horn, or dried blood. The animal 

 matter furnishes the elements of cyanogen, carbon and nitrogen, which in 

 their nascent state unite to form cyanogen, and this, seizing the potassium 

 of the potassium carbonate, forms cyanide of potassium. But the carbonic 

 acid and oxygen of the potassium carbonate are not yet accounted for. How 

 are they disposed of? They, together with a portion of the carbon evolved 

 from the animal matter, form carbonic oxide gas, which passes off. The 

 cyanide is left mingled with some refuse, from which it is separated by alco- 

 hol, which dissolves only the cyanide. 



1G6. Prussia or Hydrocyanic Acid. This acid is composed of 

 two gases, hydrogen and cyanogen, and hence its proper chemical name is 

 hydrocyanic acid. In its pure, undiluted state it is the most deadly of poi- 

 sons : a drop or two put upon the tongue of a dog causes instant death. 

 It is a colorless, limpid fluid, having a peculiar and powerful odor, like that 

 of peach blossoms and bitter almonds. The odor from these is caused, in- 

 deed, by a very minute quantity of this acid. And so, also, the flavor of 

 distilled waters of the cherry, laurel, and bitter almonds, etc., comes from 

 this acid very largely diluted. Indeed, this is an organic acid, produced in 

 certain vegetables by means of the processes alluded to in the second divis- 

 ion of this work. The chemist does not obtain this acid by extracting it 

 from the vegetable substances in which it exists in so diluted a state ; but 

 he heats certain cyanides with sulphuric acid in a distilling apparatus, and 

 collects the acid in a cool receiver. This is a dangerous experiment, and 

 we will not describe it further. 



QUESTIONS. 



140. What are the constituents of water ? What proportion of each by 

 weight and by volume ? 141. Describe a physical method of decomposing 



F2 



