142 E. F. ROEBER 



development depended rather on chemists and metallurgists, 

 who were attracted by the possibilities of the application of 

 the electric current which had proven to be such a manageable 

 and thoroughly reliable agent in other fields of engineering. 



The following sketch naturally does not aim at com- 

 pleteness, and no attempt will be made to give details of proc- 

 esses. The object is rather to bring out some general prin- 

 ciples which have manifested themselves all along during the 

 development of the electrochemical industries — leitmotives, 

 to borrow a word from Wagner's operas. At the same time, 

 we will try to arrive at a convenient classification of the whole 

 subject. One general subdivision of all electrochemical proc- 

 esses and phenomena into two large classes offers itself. In 

 the first class electrical energy is consumed to produce chemical 

 effects, while in the second class chemical energy is changed 

 into electrical energy. Thus, the second class comprises the 

 whole field of primary cells and storage batteries, while in the 

 first class we have all those more or less novel processes which 

 are now mostly thought of when one speaks simply of electro- 

 chemical and electrometallurgical industries. 



Chemical effects may be produced by means of electrical 

 energies in various ways. We can change the electrical energy 

 into heat, which is then consumed in producing the desired 

 chemical effect ; or we can change electrical energy into chem- 

 ical energy directly by electrolysis ; or we may use a combina- 

 tion of both methods; finally, a fourth method of producing 

 chemical effects is by passing an electric discharge through 

 gases. Before giving a cursory review of applications of these 

 various principles, a general remark should be made on the 

 nature of chemicals produced by such methods. 



Many of these processes consume a considerable amount 

 of electrical energy. In the discussion of furnace processes 

 from the ordinary chemical point of view, we may, of course, 

 say that the energy is expended to produce a certain tempera- 

 ture which is required to start the process. This, however, 

 does not tell the whole story. We expend a certain amount 

 of electrical energy which is lost while the process is going 

 on. What becomes of it? If the process is conducted under 

 fairly economical conditions most of the electrical energy is 



