78 SCIENCE PROGRESS 



other acid — that the only essentials for the corrosion of ordinary 

 iron are water and oxygen. It is generally believed that iron 

 must pass through a process of solution before rust is produced, 

 and so, whilst the metal is practically insoluble in pure water 

 alone, it must be soluble in the presence of oxygen. It follows, 

 then, that oxygen must bring about some alteration in the 

 conditions of the ' voltaic circle ' — commercial iron and water — 

 in such a way that a greatly increased electric current passes 

 between the electrically different parts of the iron." 



Firstly, it may be noted that Mr. Lambert here admits that 

 iron is practically insoluble in pure water; he means, of course, 

 water such as he has prepared, which cannot have been pure. 

 It may well be argued, therefore, that as it has been shown to 

 be practically insoluble in Lambertian water, iron would be 

 insoluble in pure water. 



Secondly, that he attributes very special influence to oxygen 

 — of which more presently — inasmuch as he holds that pure 

 water plus pure oxygen can attack iron in absence of acid. 



According to Mr. Lambert, the current passing between 

 electrically different parts of a piece of commercial iron in 

 (Lambertian) water may be small because of the small 

 differences of potential existing between the electrically dif- 

 ferent parts of the metal. This argument may at once be 

 disposed of, as graphite and probably other impurities in 

 commercial iron are just as effective as platinum would be. 



That a great resistance would be offered by the electrolyte 

 to the passage of the current is beyond question. And as even 

 Lambertian water offers great resistance, water would offer 

 infinite resistance ; therefore there would be no current and no 

 action if water alone were used. 



It is necessary therefore to consider what are the alterations 

 in the conditions which may be brought about by oxygen and 

 whether these be such that iron would be attacked when 

 subjected to the conjoint action of oxygen and water. According 

 to Mr. Lambert — 



" Oxygen must do one of two things — it must in some way 

 or other increase the electrical differences between the parts of 

 the metal and so increase the electromotive force or it must 

 reduce the resistance of the circuit. When a piece of com- 

 mercial iron is put into water in a vacuum, iron strives to pass 

 into solution at the relatively electropositive part of the 

 metallic surface, but hydrogen, produced by the electrolysis of 



