THE RUSTING OF IRON 



11 Dunstan and his co-workers do 

 not appear to have been aware of 

 the extreme difficulty of completely 

 excluding carbonic acid. That 

 they, in their most important ex- 

 periment, did not take adequate 

 precautions to ensure the absence 

 of carbonic acid is clearly shown, 

 for in their description of it they 

 make the significant admission 

 that on allowing oxygen to pass 

 into the vessel containing water 

 and iron ' action immediately com- 

 menced, a substance of a green 

 colour being produced, which 

 rapidly changed to the red colour 

 characteristic of rust.' No more 

 conclusive evidence that carbonic 

 acid was present in the materials 

 could be afforded than the forma- 3 

 tion of this green colour, which 

 invariably accompanies the early 

 stage of attack of carbonic acid 

 on iron in presence of air or 

 oxygen." 



After several failures to ex- 

 clude the last traces of carbon 

 dioxide, Dr. Moody succeeded 

 in devising an apparatus by 

 means of which it was found 

 possible to leave iron, oxygen 

 and water in contact during long 

 periods without even a speck of 

 rust appearing on the surface. 

 The apparatus finally adopted is 

 shown in fig 2. The side tube 

 of the distilling flask A passes 

 through the long condenser case 

 B and forms a bend at C in 

 which the piece of purified iron 

 is placed; the other end of the 



413 



27 



