W. Sxey.—Desilvering of Argentiferous Gold. 47 
destroyed. Similar disasters occurred at Waitangi, and great loss was 
occasioned. 
Art. V.—On a new Mode for the direct Desilvering of Argentiferous Gold. 
By Winuw Sxey, Analytical Chemist to the Geological Survey of 
New Zealand. 
[Read before the Wellington Philosophical Society, 25th August, 1868.] 
Tue tedious nature of the method at present employed to desilver argenti- 
ferous gold, was particularly foreed upon my attention a few weeks ago, on 
reading an account of a new patent process by which the silver is removed 
from the alloy by chlorine ejected into the mass while in a molten state, 
dependence being placed on borax as a preventative to the volatilization of 
the chloride of silver thus formed. Having doubts as to the complete 
prevention of this volatilization by borax, doubts which grew into positive 
disbelief before the results of experiments made in this direction, and 
thinking that there must be a want felt for a shorter method than that now 
in use, I sought for one which should, as in this patent process instanced, 
also effect a direct desilvering, but without producing a silver compound so 
volatile as to necessitate similar precautionary measures. 
The most promising course apparent was in some way to take advantage 
of the powerful basic properties of oxide of silver as compared to those of 
oxide of gold. Silver is, however, I believe, still considered to be quite un- 
oxidizable in the dry way, its oxide, indeed, and its salts, with volatile acid, 
suffering complete decomposition at elevated temperatures; but it occurred 
to me if, together with nascent or feebly-combined oxygen, a free or loosely- 
combined fixed acid were presented to the molten alloy, that the oxidation of 
the silver would be then effected. 
The well-known fact of the absorption of oxygen by molten silver, and 
its liberation as the metal cools, was assuring ; for though the quantity thus 
absorbed is so small as to forbid the idea of this absorption being a chemical 
one (27 equivalents of silver only absorbing 1 of oxygen), still I was con- 
vineed from this that any oxygen I might liberate in contact with the silver 
would to a certain extent be retained by it, and in a condensed form, con- 
sequently in a manner most favourable for subsequent chemical combination 
therewith. 
Acting on these suggestions, after several preliminary trials I selected 
bichromate of potash as being able singly to supply both these desiderata, 
namely, nascent oxygen and a loosely-combined acid of some fixity ; this 
salt being slowly decomposed at a white heat, with liberation of oxygen, 
sesquioxide of chromium, and chromate of potash. | 
