342 Transactions. —Chemistry. 
Supposing, however, oxidation does occur under the circumstances 
related above, this may have been induced in part by the oxygen condensed 
upon the platinum, a carbon which I used in conjunction with the mercury 
in these experiments, as the negative pole. 
Tf this should on further investigation prove to be so, the question as to 
the oxidation or otherwise of mercury in presence of oxygen and water 
alone, practically remains unsettled. So far indeed as these experiments 
- and our general knowledge of the behaviour of this metal show, it appears, 
that in alkaline solution or in water severally, mercury is probably less 
readily affected than either gold, silver, or platinum. 
The result, however, stated in this paper and in Article XLII, Page 
882, show, I think, very clearly that the metals, silver, platinum, and 
gold, readily oxidize under ordinary circumstances, though only to a 
small extent, thus the film of oxide, or rust as I may properly term 
it, which is thus formed, never acquires any notable thickness, and so 
does not manifest its presence readily to mere physical tests. But this 
limitation in thickness of such films is not due to want of, or weakness of 
affinity between the underlying metal and oxygen, but rather to the great 
solidity of these films, and their adherence to the metal, together with their 
insolubility in the liquid surrounding them, whereby these affinities very 
soon have their action permanently restrained ; contact of the metal with 
oxygen being thus cut off. Practically there is neither scaling off nor yet 
any dissolving away of the oxide, or its saline representative, as we have — 
with iron or copper, thus the underlying metal is soon completely protected. 
Possibly the knowledge that these metals are chemically acted upon by 
oxygen, may help us to explain the origin of those electric currents which 
Professor Becquerel obtained by immersing certain “‘non-oxidizable metals”’ 
-in pure water ; why should not these currents be in many cases due to the 
kind of sadction I have just described, that is to chemical action, rather 
than as Professor Becquerel attributes to ‘capillary affinity ?’”’ Not only 
this indeed, but so far as the results I have here given can be taken as 
correct, it seems certain that a number of cases of so termed mechanical - 
absorption are resolved thereby into cases of chemical absorption—chemical 
affinities being the operant power. This aspect of my subject, however, 
and certain other matters of interest in connection therewith, I forbear to 
treat for the present, as I hope to be able soon to take up this subject 
again. 
