656 SCIENCE PROGRESS 



of removing manganese sulphide — a common impurity in iron, 

 wliich apparently undergoes oxidation with particular readiness, 

 giving rise to acid. It should be added that Friend cleaned the 

 iron he used by mechanical means and assured himself at the 

 close of each experiment that the alkali had been washed off 

 the surface. 



Taken in conjunction with Moody's experiments. Friend's 

 observations afford the clearest possible proof that the presence 

 of acid is essential to rusting. The results obtained by others 

 which appear to contravene their conclusions can only be 

 ascribed to lack of success in effecting the complete removal 

 either of carbonic acid or of slag from the iron. 



It is quite clear that the engineer and builder need not 

 concern themselves in the very slightest with ions — least of 

 all whether they enjoy independent existence or not in solution : 

 this may well be left a subject of academic dispute ; indeed 

 the proper protection of iron against decay is of such supreme 

 public importance that any attempt to complicate the problem 

 by the introduction of a pretentious jargon, which even the 

 expert can fathom with difficulty and which serves mainly to 

 cloak ignorance, deserves to be visited with the most absolute 

 disapproval. Suffice it for the engineer to know that, in the 

 first place, he should " keep his powder dry " — in other words, 

 he should take every possible precaution to prevent liquid 

 films of water from collecting on iron surfaces, as such films 

 necessarily contain carbonic acid in solution, carbon dioxide 

 being present in the air at all times ; secondly, that the access 

 of acid to the iron is to be avoided on all occasions but more 

 especially if the conditions be such that water can condense 

 readily on the iron. 



The extraordinary slowness with which ideas are spread and 

 clear conceptions are arrived at is well illustrated by the 

 publication recently by Messrs. Lambert and Thomson of an 

 account of experiments on the oxidation of iron which they 

 have carried out with the greatest perseverance and manipula- 

 tive skill but obviously without any clear understanding of 

 the conditions underlying the processes of chemical change 

 and without any clear conception of the problems to be solved. 



The aim of the investigation is said to have been " to bring 



