NITROGENOUS COMPOUNDS 49 



The hydroxy acids, e.g. glycollic acid, CH 2 (OH).CO.OH, 

 exhibit the characteristic properties of alcohols as well as of 

 acids, and either or both of the hydroxyls may be replaced by 

 NH 2 . Three different types are thus derived as follows : 



CH 2 (NH 2 ).CO.OH CH 2 (OH).CO.NH 2 



(Amino-acetic acid.) (Hydroxyacetamide.) 



CH 2 (NH 2 ).CO.NH 2 



(Aminoacetamide.) 



These compounds, it will be noticed, may be referred either 

 to the type of amines or of amides previously mentioned or to 

 both at once. 



If the amines and amides be classed together, the whole 

 group may be indicated generally by the formulae RNH 2 , in 

 which R stands for any alcohol radicle or acid radicle . what- 

 ever. It is convenient to regard them here as substituted 

 ammonia derivatives because the process of replacement can 

 be continued further, and compounds of the general types 

 R 2 NH, R 3 N, and even R 4 NOH (derived from NH 4 OH) can 

 be obtained. It is scarcely necessary to add that when more 

 than one radicle is present in a compound they are not 

 necessarily, or usually, the same. 



In agricultural chemistry the term " amides " is often 

 loosely applied to all compounds which belong to any of these 

 types. There is, however, one important point of difference 

 between the compounds of the acid radicles, such as acet- 

 amide, and those of the alcohol radicles, e.g. ethylamine. The 

 former are easily saponified by the action of acids and alkalis 

 according to the equation below ; the latter are not. 



CH 3 .CO.NH 2 + H 2 O -> CH 3 .CO.OH + NH 3 



General Properties. The amides proper, e.g. acetamide, 

 are neutral crystalline substances, generally soluble in water, 

 alcohol, etc. They can be prepared in many cases by gently 

 heating the ammonium salts of the corresponding acids, 

 thus 



CH 3 .CO.ONH 4 -> CH 3 CO.NH 2 + H 2 O 



