NDS OF CAEB03S WITH OXYGEN AND MTKoiiKN 395 



CN, as the radicle of cyanic acid or hydrocyanic acid, HCN, form- 

 ing salts, for instance of mercury, which latter on being heated, as 

 Gay-Lussac showed, gives cyanogen itself, (GN) 2 . (2) As the ammo- 

 nium salt of a carboxylic acid, R(CNH 4 O 2 ), contains the elements of 

 two molecules of water, and molecular quantities are those which act 

 in reactions ; then, previously to forming a cyanogen compound, or 

 nitri/c, by parting with two molecules water, an ammonium salt ought to 

 form an. amide by losing one molecule of water : R(CO 2 NH 4 ) H 2 O= 

 R(Ci!s H 2 O). Amides are therefore compounds containing the univalent 

 amide residue, NH 2 , of ammonia, or a compound, COX 2 , in which one 

 X=R and the other =NH 2 . Such are, for instance, formamide, or the 

 amide of formic acid, (CO)H(NH 2 ), or H(CONH 2 ). The amides com- 

 pose a most numerous series of nitrogen compounds, and are obtained 

 in many ways j 33 they are met with in plants and animals, and, as 

 has already been shown, by parting with water they form nitriles or 

 cyanogen compounds, so that they serve as transitional terms between 

 R(CO 2 NH 4 ) and RON. The varieties, reactions, and properties of the 

 amides and nitriles of organic acids, and therefore also of cyano'gen 

 compounds, are, as carbon compounds, examined in greater detail in 

 organic chemistry, and here we will only dwell on the simplest of them ; 

 and, in order to clearly explain the derived ammonia compounds, we 

 will first dwell on the ammonium salts and amides of carbonic acids. 



As carbonic acid isbibasic, its ammonium salts ought to have the fol- 

 lowing composition : acid carbonate of ammonium, H(NH 4 )CO 3 , and the 

 normal carbonate, (NH 4 )jCOj ; they represent compounds of one or two 

 molecules of ammonia with carbonic acid. The acid salt appears in the 

 form of a non-odoriferous and (when tested with litmus) neutral sub- 

 stance, soluble at the ordinary temperature in six parts of water, in- 

 soluble in alcohol, and obtainable in a crystalline form either without 

 water of crystallisation or with various proportions of it. If an 

 aqueous solution of ammonia be saturated with carbonic anhydride, 

 and then evaporated over sulphuric acid in the bell jar of an air-pump, 

 crystals of this salt are separated. Solutions of all other ammonium 

 carbonates, when evaporated under the air-pump, yield crystals of this 

 salt. A solution of this salt, even at the ordinary temperature, gives 

 oft" carbonic anhydride, as do all the acid salts of carbonic acid (for 



55 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 6 )OH = 2HOH + (CO 2 C 2 H 5 ) 2 . As the nearest derivatives of 

 ammonia, the amides \vitli alkalis yield ammonia and form the salt of the acid. The 

 nitriles do not, however, give similar reactions so readily. 



