'4.06 PRINCIPLES OF CHEMISTRY 



responding with HH and HOH. Commencing with carbonic oxide, CO, 

 the formation of carboxylic acids is clearly seen from the fact that CO is 

 capable of combining with X 2 , that is of forming COX 2 . If, for instance, 

 one X is an aqueous residue, OH (hydroxyl), and the other X is hydrogen, 

 then the simplest organic acid formic acid, H(COOH) is obtained. 

 As all hydrocarbons (Chapter VIII.) correspond with the simplest, CH 4 , 

 so all organic acids may be considered to proceed from formic acid. 



In a similar way it is easy to explain the relation to other com- 

 pounds of carbon of those compounds which contain nitrogen. By 

 way of an example, we will take one of the carboxyl acids, R(CO 2 H), 

 where R is a hydrocarbon radicle (residue). Such an acid, like all 

 others, will give by combination with NH 3 an ammoniacal salt, 

 R(CO 2 NH 4 ). This salt contains the elements for the formation of two 

 molecules of water, and under suitable conditions by the action of 

 bodies capable of taking it up, water may in fact be separated from 

 R(CO 2 NH 4 ), forming by the loss of one molecule of water, amides, 

 RCONH 2 , and by the loss of two molecules of water, nitrites, RCN, 

 otherwise known as cyanogen compounds or cyanides?* If all the 

 carboxyl acids are united not only by many common reactions but 

 also by a mutual conversion into each other (an instance of which 

 we saw above in the conversion of oxalic acid into formic and carbonic 

 acids) one would expect the same for all the cyanogen compounds also. 

 The common character of their reactions, and the reciprocity of their 

 transformation, were long ago observed by Gay-Lussac, who recog- 

 nised a common group or radicle (residue) cyanogen, CN, in all of 

 them. The simplest compounds are hydrocyanic or prussic acid t HCN, 

 cyanic acid, OHCN, and free cyanogen, (CN) 2 , which correspond to the 

 three simplest carboxyl acids : formic, HCO 2 H, carbonic, OHCO 2 H, 

 and oxalic, (CO 2 H) 2 . Cyanogen, like carboxyl, is evidently a mon- 

 atomic residue and acid, similar to chlorine. As regards the amides 

 RCONH 2 , corresponding to the carboxyl acids, they contain the 

 ammoniacal residue NH 2 , and form a numerous class of organic com- 

 pounds met with in nature and obtained in many ways, 33 but not 



32 The connection of the cyanogen compounds with the rest of the hydrocarbons by 

 means of carboxyl was enunciated by me, about the year 1860, at the first Annual Meeting 

 of the Russian Naturalists. 



33 Thus, for instance, oxamide, or the amide of oxalic acid, (CNH 2 O) 2 , is obtained in, 

 the form of an insoluble precipitate on adding a solution of ammonia to an alcoholic 

 solution of ethyl oxalate, (CO 2 C 2 H 5 )2, which is formed by the action of oxalic acid on 

 alcohol: (CHO 2 )2 + 2(C 2 H 5 )OH = 2HOH + (CO2C2H $ ) 2 . As the nearest derivatives of 

 ammonia, the amides treated with alkalis yield ammonia and form the salt of the acid. 

 The nitriles do not, however, give similar reactions so readily. The majority of amides 

 corresponding to acids have a composition RNH 2 , and therefore recombine with water with 

 great ease even when simply boiled with it, and with still greater facility in presence oi 



