150 MODERN SCIENCE READER 



(I) Electrolytic Apparatus. 

 (II) Electric Arcs and Discharges in Gases. 

 (Ill) Electric Furnaces. 



7. Electrolytic Apparatus 



Electrolytic apparatus and processes use or utilize the 

 separating or decomposing power of the electric current. 

 Whenever an electric current is sent through a liquid ma- 

 terial which is compound in its nature, i. e., a chemical 

 compound, the current tends to decompose the compound 

 into two constituents, appearing respectively at the two 

 points of contact of the electric conducting circuit with 

 the liquid in question, i. e., at the surface or face of con- 

 tact of the undecomposable conducting part of the circuit 

 with the decomposable part. If the current has a definite 

 direction the constituents appear at definite electrodes. The 

 action is simply the result of the current extracting (or 

 tending to extract) from the electrolyte one of its constit- 

 uents at each of the two electrode surfaces. All subse- 

 quent changes following upon this primary tendency of 

 the current are called secondary reactions, and are prac- 

 tically simultaneous with the primary. These may even 

 be regarded as truly primary reactions also, the primitive 

 decomposing or separating power of the current passing 

 being regarded only as a tendency or a determining cause 

 which practically results in the reactions actually taking 

 place. 



This agency is an extremely vigorous and potent force 

 for producing chemical transformations. It enables us, for 

 instance, to split up some of the strongest chemical com- 

 pounds into their elementary constituents, to convert cheap 

 materials, in short, to perform easily some very difficult 

 chemical operations, and in some cases to perform chemical 

 operations otherwise impossible. A description of all these 

 various processes would take a volume, but a short explana- 

 tion of a few of them will make the principles clear and 

 suffice for my present purpose. 



