122 CHEMICAL PROPERTIES AND COMPOSITION 



HN CO 



I I 

 OC C-NH\ 



I II >co 



HN C NH/ 



Unfortunately all these observations are merely qualitative, 

 and are often interfered with by other causes, as in the 

 strongly acid character of formic acid, H 2 C0 2 , as compared 

 with carbonic, H,CO 3 . 



(c) Influence of Nitrogen. 



(a) The Cyanogen Group. The negative character of 

 nitrogen is best seen in derivatives which contain nitrogen 

 as such (not with hydrogen or oxygen), and consequently 

 triply linked to carbon in the cyanogen group : 



N = C- 



If the element in question has hydrogen attached, forming 

 the amido group (NH 2 ), its negative character is weakened 

 and is hardly recognizable, or it may even be reversed. If 

 it has oxygen attached as in the nitro group (NO 2 ), the 

 acid character is indeed sharply marked, but it remains 

 uncertain whether it is to be ascribed to the oxygen or the 

 nitrogen. Therefore we shall first consider the behaviour 

 of the cyanogen group. 



In the simplest case, combined with hydrogen to form 

 hydrocyanic acid 



N = C H, 



it is apparent that this tendency, caused by nitrogen, of the 

 cyanogen group to attract negative electricity results in 

 the formation of positive hydrogen ions, i. e. of an acid. 



Taking then a somewhat less simple case, we may com- 

 pare cyanic acid with water, 



NCOH, HOH, 



the entry of cyanogen produces here the same effect as 

 that of chlorine, which converts water into a weak acid 

 hypochlorous acid. 



