ACIDS, BASES, AND SALTS 171 



1. Every acid contains hydrogen, combined with one or more 

 other atoms,~constituting a group called a radical. 



2. The very same radicals, such as S0 4 , appear also in a num- 

 ber of salts. 



3. Every base contains OH (the radical hydroxyl), and usually 

 one atom, but occasionally more than one (as in NH 4 ) in the 

 other radical. 



4. The same radicals that are combined in bases with OH 

 appear also in numerous salts. 



5. Radicals may be simple, like H, Na, and Cl, or compound, 

 like S0 4 and NH 4 . 



Positive and Negative Radicals. When the electric cur- 

 rent is passed through an aqueous solution of an acid, such as 

 hydrochloric acid (p. 55), the acid is decomposed and hydrogen is 

 liberated at the negative electrode. Since this electrode attracts 

 positively charged particles, hydrogen is called a positive radical. 

 (In all circumstances, unlike charges of electricity attract, and 

 like charges repel one another.) The rest of the acid molecule, 

 such as Cl, is attracted to the positive electrode, and is therefore 

 called a negative radical. Similarly, when we electrolyze a solu- 

 tion of a base, such as sodium hydroxide, oxygen is always liber- 

 ated at the positive electrode. This is due to the decomposition 

 of the hydroxyl radical OH, which is consequently also a negative 

 radical. 



40H -* 2 + 2H 2 0. 



The rest of the alkali molecule, such as Na, is attracted to the 

 negative electrode and is therefore a positive radical. 



In the same way every salt contains a positive radical, other 

 than H, combined with a negative radical, other than OH. The 

 name of each salt indicates the radicals of which it is composed. 



As regards the salts in the second column, they show positive 

 radicals, like K, Zn, and Na, found in the list of bases. The 

 negative radicals C1O 3 , S, 2 , and CO 3 are not in the list of acids 



