IV.—CHEMISTRY. 
Arr. XLII.—On the Oxidation of Silver and Platinum by Oxygen in presence 
of Water. By Wr.t1am Sxey, Analyst to the Geological Survey of New 
Zealand. 
[Read before the Wellington Philosophical Society, 29th January, 1876.] 
I saat confine myself in this paper to a statement of results, and the 
considerations which led me to seek them, as I intend leaving the discussion 
of these in their various relations to certain debateable subjects for another 
opportunity, my investigations upon this matter being as yet incomplete. 
A knowledge of the fact that gold and platinum readily combine with 
sulphur at a common temperature, and that the compounds thus formed 
cannot be detected by mere physical tests, suggested to me that oxygen 
may also combine with these metals under conditions somewhat similar, 
and in this manifesting none of the more distinguishing signs of chemical 
action, has consequently to this time been overlooked. 
Acting at once upon this suggestion, I fortunately made a series of 
experiments to test the correctness or otherwise of my suspicion, and the 
results of these experiments, showing them in the main, I believe, to be 
correct, I submit to your notice. 
I should premise my statement of these results by informing you, in 
- anticipation of what will in due course appear, that one of my principal 
tests for the oxidation of these metals is that known as the ‘‘ mercury test,” 
by which it will perhaps be remembered I had the honour of demonstrating 
before you experimentally the sulphurization of gold by sulphuretted 
hydrogen ; and that this test is based upon the fact that mercury readily 
amalgamates with silver or platinum when in contact with them, but that 
if the minutest film of any substance intervenes between the two metals, 
amalgamation is either retarded or altogether prevented ; thus, by the aid 
of this test, minute quantities of a substance enfilming either of these 
metals may readily be detected. 
Commencing with silver, I ascertained the following facts regarding it: 
1. That pure silver immersed for a few hours in distilled water or in 
the purest water I could obtain, has its surface so modified that 
it will not amalgamate immediately afterwards. 
2. That such an effect is not produced when either rain or spring 
water is used. 
