ELECTROCHEMISTRY — RICHARDS. 169 



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 material which is compound 

 in its nature, i. e. ; a chemical compound, the current tends to decom- 

 pose 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 contact of the 

 undecomposable conducting part of the circuit with the decompos- 

 able 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 constituents at each of the two electrode surfaces. All 

 subsequent changes following upon this primary tendency of the 

 current are called secondary reactions, and are practically simul- 

 taneous 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 produc- 

 ing chemical transformations. It enables us, for instance, to split 

 up some of the strongest chemical compounds into their elementary 

 constituents, to convert cheap materials into much more valuable 

 derivatives, to purify impure 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 explanation 

 of a few of them will make the principles clear and suffice for my 

 present purpose. 



Electrolysis of water. — As a raw material, water may be said to 

 cost nothing. Apply an electric current to it in the proper way, 

 and it is resolved into its constituent gases, hydrogen and oxygen, 

 as cleanly and perfectly as anyone could desire. These gases have 

 many and various uses, and are valued each at several cents per 

 pound. A whole industry has thus grown up, based on the simple 

 electrolysis of water, to supply these two gases for various industrial 

 uses. Europe possesses many of these plants; there are a few in 

 the United States. The speaker has translated from the German 

 a small treatise on this industry. 



Electrolysis of salt. — Common salt, sodium chloride, is one of 

 the cheapest of natural chemicals. It has some uses of its own, 

 but centuries ago chemists and even alchemists devised chemical 

 processes for transforming it into other sodium salts, such as caustic 



