THE RUSTING OP IRON AND STEEt. 
260 
In the first place I think I am rightlin saying that when zinc and water are 
brought into contact there is actually produced peroxide of hydrogen ; there we 
have an evidence of the formation of this peroxide of hydrogen which according 
to Professor Dunstan’s theory is the precursor of the oxidation of iron. It is 
difficult or perhaps impossible to detect the presence of peroxide of hydrogen 
when iron is rusting, because, as Professor Dunstan has shown us, directly per¬ 
oxide of hydrogen in an alkaline solution is brought into contact with metallic 
iron you have decomposition of the peroxide of hydrogen. 
Another point that Professor Dunstan touched upon, but rather doubtfully, 
was whether electrolysis had anything to do with rusting. I think that his ex¬ 
periments distinctly prove that electrolysis is one of the great and most important 
facts connected with the oxidation. For example, in the case of those bodies 
which are inactive in preventing oxidation or rather which accelerate rusting, 
their presence would improve the conductivity of the water, electrolysis would 
take place more rapidly, the current would pass more rapidly through a solution of 
these salts than through pure water and therefore there would be a hastening of 
the oxidation. 
The fact of the necessity of liquid water to start or maintain the rusting is very 
certain and there are many facts which prove this; you will all know that after 
a dewy night bright railway rails which have been used on the previous day are 
covered with a thin coating of rust which is formed no doubt in consequence of 
the decomposition of the small quantity of dew on the surface of the iron. I had 
a remarkable instance of this in my own house some little time ago ; I had a 
Wenham burner which was not burning properly, the ventilator from it was 
apparently stopped; on opening the outside casing which surrounded the iron 
tube which carried off the products of combustion, we found that near the burner 
the iron was in perfect condition but a few feet away and near the chimney into 
which the pipe enters the iron was entirely corroded away. It was not the place 
where we might have expected it, where the temperature was high and there was 
more chemical action, but it was at the place where the temperature was low and 
where the water vapour produced by the combustion, would have been deposited. 
Then there is another point that Professor Dunstan did not mention and which 
I think rather supports his theory. Many years ago, when I was assistant to 
Professor Frankland at the Boyal Institution, I was well acquainted with the 
cubes of iron and steel which Faraday had placed in different solutions and some 
years after that I put up a number of specimens myself, which Professor Dunstan 
has seen; and on looking at these after their having stood there for some years, 
on just shaking the bottle one found curious dark streaks which looked like 
ferrous oxide being transformed through magnetic oxide into ferric oxide. Now 
ferrous oxide, according to Professor Dunstan, is a precursor of the formation of 
rust and therefore this greenish deposit is still further in support of his doctrine. 
I must say that I myself feel very much convinced that Professor Dunstan is 
perfectly right in saying that peroxide of hydrogen is connected with the subject 
but I should like to ask him one question, the reply to which I shall not how¬ 
ever be able to stop to listen to, and that is whether he has analysed the oxide of 
zinc formed by oxidation of zinc in contact with peroxide of hydrogen. P 
The stopping of rusting of iron by a powerful oxidising agent such as chromic 
[ acid is very remarkable. You have there a body which is very likely to give off 
oxygen to anything that will combine with it, and yet the piece of polished steel 
or iron remains bright in a strong solution of chromic acid. I thought when 
Professor Dunstan first told me of it that it would be an excellent question to 
set in Examination Papers “ What is the action of chromic acid upon iron,” and 
I remember asking a celebrated chemist what would happen ? He entered into a 
