THEORY OF ELECTROLYTIC DISSOCIATION, ETC. 199 



The electromotive force required decreases from the potassium end of the 

 series to the gold end. If the metals are arranged in a series according to the 

 decreasing intensity of their chemical activity in the free state toward other 

 substances, the same order is observed as that in the above series. Metals 

 higher up in the series will displace others following from solutions of their 

 salts, but not vice versa. All the metals, from potassium to hydrogen, will 

 displace hydrogen from dilute acids, but those following hydrogen will not. 

 The metals, down to copper inclusive, will rust in the air. The oxides of the 

 metals, down to manganese inclusive, cannot be reduced to the metal by heat- 

 ing in hydrogen, but oxides of cadmium and the metals following can. The 

 metals down to hydrogen do not occur in the free state in nature. 



The non-metals and negative radicals into which they enter (acid radicals) 

 can also be arranged into a similar electronegative series. 



Discociation theory applied to acids, bases, salts, and neutral- 

 ization. 



Acids. A general discussion of acids, bases, and salts is given in Chapter 

 8. In terms of the ionic theory, acids are substances which give positive hy- 

 drogen ions in solution, associated with negative ions tbat may be either 

 simple, as OF, or complex, as SO/', or CO 3 // . The properties common to all 

 acids are due to the hydrogen ions ; for example, sour taste, action on litmus, 

 action on metals with displacement of the hydrogen. The latter action is rep- 

 resented in the case of zinc by the ionic equation, Zn + 2ET -|- SO/' = Zn** 4- 

 SO 4 " + H 2 . This stands as a type for all acids, and it will be observed that 

 the action is essentially between the metal and hydrogen ions, and is independ- 

 ent of the negative ion. The charges on the hydrogen ions are transferred to 

 the zinc atoms, which then become ionic, and the discharged hydrogen ions 

 escape as molecules. 



The specific properties of the acids in solution are due to the different com- 

 position of the negative radicals. These radicals are the same whether acids 

 or their salts are used. When a solution of silver nitrate is added to one of 

 potassium chloride, a white precipitate of silver chloride is obtained, but when 

 added to potassium chlorate in solution, no visible change takes place. Both 

 of these salts contain chlorine, but the first gives the ion CK, and the second 

 the ion CIO/. In other words, the composition of the negative radicals is 

 different, which results in a different behavior toward the positive silver ion. 

 Silver chloride is an insoluble substance and is formed in solutions only when 

 silver ions and chlorine ions are brought together. Chlorine ions are formed 

 only from hydrochloric acid or the chlorides. Silver chlorate is a soluble 

 body, and, therefore, nothing that we can see happens when silver ions and 

 chlorate ions are brought together in solution. 



Independence of ions. The above discussion leads to the conclusion 

 that the ions of acids are distinct substances with individual physical and 

 chemical properties. Each kind of ion behaves as if it were alone present in 

 the solution. This is true of all ions. To illustrate, two instances may be 

 given that have to do with a physical property, namely, color of salts or acids. 

 All copper salts of colorless acids have a blue color in dilute solutions. The 

 blue color is due to the copper ion, and all copper salts that are soluble give 



