THEORY OF ELECTROLYTIC DISSOCIATION, ETC. 191 



of acids hydrogen is readily separated in chemical actions from the 

 rest of the molecule, which is a radical, consisting of a non-metallic 

 element, or a group of atoms acting as a unit and remaining intact. 

 In electrolysis, division occurs in the same manner, hydrogen sepa- 

 rating at the cathode, and acid radical being attracted to the anode. 

 Salts behave in the same manner as acids in regard to the division 

 of the molecules, which is only what we should expect, since they 

 are so closely related to acids. Indeed, some chemists put both in 

 the same class, regarding acids as salts of hydrogen. Bases in chemical 

 action and in electrolysis show a division between the metal and 

 the hydroxyl (OH) radical, the metal going to the cathode, and the 

 hydroxyl radical to the anode. It appears, then, from the side of 

 chemical action as well as that of electrolysis that an aqueous solution 

 of an acid contains positive hydrogen ions and negative acid radical 

 ions; a solution of a salt contains positive ions of a metal and negative 

 acid radical ions; and a solution of a base contains positive ions of a 

 metal and negative hydroxyl ions. 



Ions and atoms not the same. The student should note partic- 

 ularly that a substance in the ionic state is quite different from the 

 substance in the free state. Simple ions are atoms plus a charge of 

 electricity, while atoms of free elements are not charged, and this 

 difference is sufficient to account for the difference of behavior. 

 Thus, when sodium chloride (NaCl) is dissolved in water, many of 

 the molecules break up into Na-ions and Cl-ions, but there is tio 

 chemical action between the water and Na-ions or Cl-ions, whereas 

 sodium in the free state acts violently on water, and chlorine dissolves 

 in water with some chemical action and imparts its odor and bleach- 

 ing properties to the water. A solution of sodium chloride has no 

 odor or bleaching action. 



Symbols representing- ions. Ions are represented by the usual 

 chemical symbols, with the addition of marks to indicate positive and 

 negative charges. Thus, Na + , or Na', stands for a positively charged 

 sodium ion, and Cl~, or Cl', stands for a negatively charged ion of 

 chlorine. Quantitative experiments in electrolysis show that the 

 amounts of electricity possessed by ions is proportional to the valence 

 of the atoms or radicals constituting the ions. If the charge on a 

 sodium or on a chlorine ion is taken as the unit charge, then the 

 charge on an ion of a bivalent atom or radical is two units, and is 

 represented thus, Ca ++ , or Ca", and SO7~, or SO/'. The ion of 

 trivalent aluminum is written Al +++ , or Al" ', etc. 



