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THE EXISTING OF IEON AND STEEL. 
- BY — 
WYNDHAM R. DUNSTAN, M.A., F.R.S., 
Secretary to the Chemical Society and Director of the Scientific 
Department of the Imperial Institute. 
{Summary of a Lecture delivered at the Royal Artillery Institution, Woolwich, 
Thursday 24th Feb.. 1898.) 
Colonel E. Bainbridge, c.b., R.A., in the chair. 
I T is well known that a piece of iron or steel exposed to air soon 
becomes covered with a reddish crust, which involves a corrosion 
and gradual eating away of the metal 
This reddish crust, rust, is essentially an oxide of iron containing 
combined water, practically identical with the well-known jeweller’s 
rouge, which is nearly pure ferric oxide Fe 2 0 3 . The ordinary chemical 
explanation of the process is that the iron, having a great affinity for 
oxygen, combines with the oxygen of the atmosphere, and thus rust 
is formed, the change being expressed by the chemical equation 
2 Fe, + 30q = 2 jFe 2 0 3 , or if the combined water be taken into account 
Fe 2 +30 + 311,0 = Fe 2 0 3> 3H 2 0. 
Scientific chemists, however, are aware that there are certain 
circumstances connected with rusting which indicate that the action 
in reality is not so simple as these equations represent. It has been 
known for many years that if iron is placed in contact with alkalis it 
does not rust. The explanation which has been suggested, and 
generally accepted by chemists, of this peculiarity, is that carbonic 
acid gas ((70 2 ) is intimately concerned in rusting; in fact it has been 
asserted that without carbonic acid gas (which is present in air) 
rusting cannot occur. Alkalis, by absorbing and removing carbon 
dioxide, prevent rusting. This, as I have said, is the generally 
accepted view of the chemistry of rusting, which has been summarized 
by Professor Crum Brown, by the two following equations :— 
(1 ).—4 (Fe J- HfO + CO^) = 4 FeC0 3 + 4 H 3 . 
(2 ).-4 FeCO 3 + 6E % 0 + 0 2 = 2 Fe, ( OH) G + 4 CO,. 
A few years ago I determined to investigate more closely the 
