CORROSION OF IRON AND STEEL, ETC. 63 



accelerates corrosion. This is what one would expect. There is no 

 corrosion where a current flows to a pipe, as from tram lines. 

 Another accidental case of corrosion is that due to particles of 

 dirt, especially oil, getting into water, and thus on to the surface 

 of iron, giving rise to an unusual amount of electrolytic action. 



The corrosion of different forms of iron and steel appears as 

 somewhat irregular, and varies according to the conditions to 

 which the iron is exposed. It is usually possible to repeat a 

 corrosion experiment with precisely the same result if the con- 

 ditions are the same, but if any of the conditions are not the same, 

 and vary in what appear to be quite trivial particulars, then widely 

 different results are often obtained. Messrs. Hehn & Bauer (see 

 above) find for instance that cast iron and malleable iron are equally 

 corroded in distilled water if this is at rest. If the water is kept 

 in motion then the cast iron is most corroded. On the other hand, 

 there is no difference between the irons as regards corrosion in 

 moving salt water. It is due to facts like these that uncertainty 

 may be said to exist as regards corrosion of iron. 



Iron corrosion has points of similarity with the corrosion of 

 other metals, but it is to be looked on as exceptional among metals 

 for the following reasons : — 



(1) Iron is more heterogeneous, physically and chemically, 

 than any other metal used commercially. It contains many im- 

 purities. It occludes gases (especially hydrogen) in an especial 

 degree. 



(2) The rust which forms from iron is not an adherent coating, 

 and does not protect the metal from further corrosion. 



(3) Ferrous compounds, which are formed as intermediate 

 products in rusting, are powerful catalytic agents on certain re- 

 actions, and possibly on part of the rusting process. 



(4) The property of being made passive, while it does not 

 appear at present to bulk largely in corrosion problems, makes 

 iron stand out from the metals as exceptional. 



2.— THE UTILISATION OF GASES IN MODERN INDUSTRIAL LIFE 

 By GEORGE MARKER, D.Sc, Sydney 



I HAVE chosen as the subject of my paper the utilisation of Gases 

 in Modern Life, because of the rapidly extending application 

 of these hght and invisible substances to every department of 

 human activity. It would not be possible withm the compass of 

 a short paper to deal with all the uses to which gases are nowadays 

 put, even had I the necessary knowledge, so many and varied 

 are their applications, and I shall content myself with describing 

 the most important. 



Putting on one side the use of air as a means of sustaining life 

 and the processes of combustion, since these can hardly be con- 

 sidered as human applications, the uses of gases for illuminating 



