ACTION OF WATER ON IRON. 255 



The resulting combination, the oxidum, ferroso-ferrique of 

 Berzelius, is, according to him, by long continued watering, 

 converted all into a h3^drated peroxide (FcgOg + 2 HO). Gay 

 Lussac, however, states, that it is impossible to oxidate iron to 

 its maximum by the action of water, which seems most proba- 

 ble. He states the composition of the oxide produced at 37*8 

 per cent, of oxygen, which approaches that of the native mag- 

 netic oxide. Neither iron nor its oxides are at all soluble in 

 pure water according to Westrumb. 



Of the Action of Dry Air upon Iron. 



5. Perfectly dry air has no action whatever on iron, nor has 

 dry oxygen below ignition, unless we consider the " blueing " 

 of steel as a state of oxidation. Both air and oxygen rapidly 

 decompose iron at and above the temperature of ignition, pro- 

 ducing, according to Berthier, sesqui-oxide of iron, quadri-pro- 

 toxidated = F Cg O3 + 4 F e O. 



Mosander's results, however, do not agree with these j he 

 found, that iron oxidated by dry air, at a red heat, produced an 

 outer coat of sesqui- or peroxide, and beneath this, one having 

 the composition (F Cg O3 + 6 F e O). 



The extreme slowness with which moderately dry air acts on 

 iron is evidenced by an experiment of M. Zumstein, who fixed 

 a polished iron cross on the summit of Monte Rosa, in the Alps, 

 in August in 1820: on visiting it again, in August, 1821, it 

 was found neither rusted nor corroded, but had merely acquired 

 a tarnish the colour of bronze. The temperature of the air was 

 21" Fahr. Barometer, 16 inches 42 lines, and height above the 

 level of the sea, 14,086 feet. — [Bib, Univer. xxxiii. p. 65.) 



6. Of the Action of Air and Water combined on Iron. 



While at common temperatures, both air and water are sepa- 

 rately strictly neutral bodies in respect of iron ; yet when acting 

 conjointly, the case is widely different. In general it may be 

 stated that any neutral body, however slight its own electro- 

 positive or negative relations may be in presence of iron and 

 oxygen, will modify the action of these bodies on each other 

 in proportion as it tends to render the oxygen more negative 

 and the metal more positive. 



7. It must be confessed that there are many points in the ac- 

 tion ef air and water combined still in need of being experi- 

 mentally cleared up. We are enabled, however, to discern the 

 general nature of the phenomena. We are to be understood as 

 speaking, in the first instance, of wrought and malleable iron, 



