OTHER PROPERTIES OF ELECTROLYTIC SOLUTIONS 315 



In aqueous solutions, with a few exceptions, the acids are substances 

 in which the hydrogen is joined to an electronegative group through an 

 oxygen atom. For example, in the case of acetic acid we have 

 CH 3 COO-H + . Such acids are known as hydroxy-acids, or perhaps 

 better aquo-acids, as Franklin has suggested. Similarly, in the case of 

 ammonia, substances in which the hydrogen atoms are connected to an 

 electronegative group through the intermediary of a nitrogen atom are 

 acids. This is a class of substances commonly known as the acid amides 

 or imides. Thus, we have, corresponding to acetic acid CH 3 COOH, 

 acetamide CH 3 CONH 2 . Acetamide is therefore an acid related to am- 

 monia as acetic acid is to water, and, according to Franklin, may be 

 called an ammono-acid. 46 In view of the fact that nitrogen is tri-valent, 

 the acid amides are dibasic acids in contrast with the corresponding aquo- 

 acids which are mono-basic. As we have seen in an earlier chapter, the 

 acid amides are soluble in ammonia and many of them are excellent con- 

 ductors of the electric current. It has been shown that the acid amides 

 and imides in ammonia possess characteristic acidic properties; that is, 

 they react with the metals to form salts and hydrogen and with .bases 

 to form salts and ammonia. Thus we have: 



Mg + CH 3 CONH 2 = CH 3 CONMg + H 2 , 



a reaction similar to that obtained with acetic acid in water. The acid 

 amides likewise react with bases in ammonia to form salts and water; 

 for example, 



CH 3 CONH 2 + (CH 3 ) 4 NOH = CH 3 CONH(CH 3 )<N + H 2 O. 



Acid amides in ammonia solution are weaker acids than the correspond- 

 ing oxy- acids are in aqueous solutions, but this is to be expected, since 

 the dielectric constant of ammonia is much lower than that of water and 

 the ionization of all electrolytes is lower in ammonia than in water. 

 However, as may be seen from the conductance values for the acid amides 

 in ammonia solution as given in an earlier chapter, the ionization of 

 certain of these acids in ammonia is as great as that of typical salts in 

 this solvent. Relatively, therefore, the acid amides are as strong in 

 ammonia as ordinary acids are in water. It is interesting to point out, 

 in this connection, that, while the acid amides throughout exhibit acidic 

 properties in ammonia solution, it is only in exceptional cases that they 

 exhibit marked acidic properties in water. The reason for this is not 

 well understood, but it seems probable that, when the acid amides are 



48 Franklin, Am. Chem. J. 3fi, 285 (191-2). See also numerous other articles by the 

 same author in the Am. Chem. J. and J. Am. Chem. Soc. 



