ACTION OF WATER ON IRON. 25/ 



11. It has been doubted by Marshall Hall and others, who 

 assert that nothing but nitrogen is evolved, whether water is 

 ever decomposed by iron at common temperatures, though in 

 presence of air ; but independent of the conclusive and simple 

 experiment of Guibourt, of mixing in large bulk iron turnings 

 and water, and collecting the hydrogen, Becquerel is of opi- 

 nion, that the existence of ammonia in the oxides produced, 

 which was first detected by Vauquelin, is corroborative of the fact, 

 inasmuch asthe water must suffer decomposition as well as the 

 air, in order that the hydrogen and nitrogen may combine to 

 form ammonia. Chevallier and Bousingault also found ammonia 

 in the native oxides of iron ; and Austin states, that it is always 

 present when iron is oxidated by air and water. {Ann. de Chim. 

 vol. xxxiv. p. 109.) Too much stress, however, cannot be laid 

 upon this argument, as it has been found that rust, in common 

 with other porous bodies, greedily absorbs ammonia and many 

 other gaseous substances. 



12. When the action of air and water on iron has taken place 

 with sufficient slowness, the resulting oxides are found crystal- 

 lized in the form of the native octohedral iron ore. Becquerel 

 describes a case of crystals, of both hydrated and anhydrous 

 peroxides, found united in one specimen of corroded wrought 

 iron from an old chateau of the ninth century. The hydrated 

 oxide would seem here to have been formed first, and after- 

 wards decomposed by the action of the still unchanged iron 

 upon its water. 



13. When water contains foreign admixture, the composition 

 of the rust resulting from its action varies accordingly, together 

 with the rapidity of its corrosion ; thus, when it contains car- 

 bonic acid, the rust contains water and subcarbonate of iron, 

 according to Dr. Thomson ; and Soubeiran found rust under 

 such circumstances, formed of the sesquioxide, combined 

 with 3 atoms of water, and containing variable quantities of the 

 sesqui-basic carbonate of iron, and occasionally the carbonate of 

 the protoxide. Carbon is always, silica occasionally, deposited 

 from the iron dissolved. 



14. With the exception of those bodies which are occasionally 

 met with in mineralized waters, and of carbonic acid, and the 

 constituents of sea water, that rendered foul by decaying organic 

 matter, and that from mines, all others are rather beside our 

 present object, as modifying the action of air and water on iron. 



We proceed, then, to consider the nature and results 



Of the Action of Sea Water on Iron 

 at ordinary temperatures ; and although the results of the careful 



