650 SCIENCE PROGRESS 



" Rusting of Iron primarily due to Attack by Hydrogen Ions. — 

 This point established, it becomes apparent that the rusting of 

 iron is primarily due not to attack by oxygen but by hydrogen ions." 



In the interest of engineers and others not versed in the 

 scientific jargon of the day, who wish to have explanations 

 given in plain terms, it is clearly desirable to consider what is 

 meant by such statements. 



The cult of the free and independent ion has so dominated 

 most branches of physical and biological science during the 

 past twenty-five years that it may almost be ranked with 

 influenza and plague as one of the infectious complaints that 

 have been brought into prominence in modern times. The 

 manner of its development is very remarkable. 



Having made the fundamental discovery that compound 

 substances which are decomposed by an electric current are 

 resolved into two parts, Faraday in 1834 coined the word ion 

 simply to express " those bodies which can pass to the 

 electrodes in electrolysis." 



It was not until 1857 that Clausius postulated the conception 

 that probably some of the encounters that take place between 

 the moving compound molecules in a liquid are so violent that 

 some of the molecules are broken up into their constituent 

 atoms. To explain electrolysis, he assumed that when an 

 electromotive force is applied to a liquid it does not produce 

 disruptions and reunions but finding these already going on 

 influences the motions of the parts during their intervals of 

 freedom, so that the positive move more in the positive 

 direction and the negative move more in the negative direc- 

 tion than would be the case if they were uninfluenced. 

 Clausius apparently did not suppose that compounds were 

 broken up only into their ions ; indeed, on his kinetic 

 hypothesis it is difficult to see why all of the atoms in a 

 compound should not make their separate appearance at the 

 electrodes — why all compounds which undergo electrolysis 

 should always be broken up in a particular way into two 

 ions only, the one being always hydrogen or a metal, the 

 other whatever is associated with the hydrogen or metal in 

 the compound ; furthermore why so many compounds- 

 organic compounds in particular — should not be in the least 

 affected by an electric current, The fact that, in so many 



