STRUCTURES RESEMBLING ORGANIC GROWTHS. 175 



indifferent conductor, e. g., carbon or platinum, which is im- 

 mersed in a solution of an electrolyte, e. g., NaCl. The ferrous 

 salt may be in contact with only one region of the platinum 

 wire, e. g., one of its extremities; if now an oxidizer (e. g., chlorine, 

 bromine, nitric acid, etc.) be brought in contact with the other 

 end of the wire, the ferrous salt is at once oxidized to ferric. 

 The subjoined diagram (Fig. i) will illustrate, in which chlorine 

 is regarded as the oxidizer. The rate of the process depends 

 upon the concentrations of the FeCl 2 and C1 2 at the electrode 

 regions, the area of the electrodes, and the electrical conductivity 

 of the circuit. Each atom of chlorine reaching the wire at region 

 B causes instant oxidation of a molecule of FeClo to FeCls; 

 i. e., each ferrous ion (Fe ++ ) becomes a ferric ion (Fe +++ ) by 

 receipt of a positive charge from the wire; this charge comes 

 from the chlorine atom w r hich releases it to the wire, becoming at 

 the same time a chlorine ion (Cl~) . The number of chlorine 

 ions in solution thus necessarily increases at the same rate as 

 the number of ferric ions, and the only evident chemical changes 

 are those occurring at the contact of the oxidizing and reducing 

 substances with the wire. The current (positive stream) flows 

 in the solution from the iron salt to the chlorine, and a certain 

 process of rearrangement or change of ionic partners may be 

 conceived as taking place throughout the whole intervening 

 stretch of electrolyte-solution. 1 



The above account will indicate sufficiently the general char- 

 acter of the physical and chemical changes taking place in any 

 oxidation and reduction cell. At the anodic area Fe ++ ions are 

 oxidized to Fe +++ ions; at the cathodic area electrically neutral 

 chlorine atoms are reduced to Cl~ ions. The wire serves simply 

 to convey electricity from the one region to the other. Similarly 



1 It is impossible to give a full exposition in this place, and the reader is referred 

 to the textbooks of electrochemistry (Arrhenius, LeBlanc, Liipke, etc.) for a more 

 detailed treatment. The electron theory includes all of the above phenomena as 

 special cases. From the standpoint of this theory it is more correct to regard each 

 Fe ++ ion as yielding an electron (negative charge) to the wire at region .4; this 

 displaces a corresponding electron at B; this electron is taken up by the Cl atom 

 which thus becomes a Cl~ ion. The flow of electrons constitutes the current in the 

 wire; at the electrodes there is equal and simultaneous loss and gain of electrons by 

 the substances (ions or other dissolved substances) at anode and cathode respec- 

 tively. 



