I Y. — CHEMISTRY. 



Art. LI. — On the Mode of Producing Auriferous Alloys hy Wet Processes. 

 By W. Skey, Analyst to the Geological Survey of New Zealand. 



[Read he/ore the Wellington Philosophical Society, 2^rd October, 1872.] 



In former papers read before tins Society* I showed that metallic sulphides 

 generally reduced gold from both acid and alkaline solutions ; that silver as 

 nitrate was reduced by galena and sulphide of copper, but not by iron 

 pyrites, while its ammoniated solutions were unaffected by any of the sulphides 

 experimented with ; and from a consideration of these results I suggested 

 that most of our native deposits of noble metals have been formed by the 

 agency of metallic sulphides, and not by that of organic matter as has hitherto 

 been generally supposed. 



The question which naturally presented itself to me at the time as to the 

 capability of processes of this nature producing alloys of such metals (as found 

 in nature) was tacitly left over for consideration until the behaviour of these 

 sulphides with metallic solutions should be more fully examined. 



In pursuit of this question as to the possibility of obtaining mixed metallic 

 deposits or alloys by the agency of metallic sulphides I have from time to 

 time, as opportunity offered, studied the behaviour of different sulphides when 

 in contact with various salts of gold and silver, and the principal results 

 thus obtained I now beg to state. 



1. That solutions of chloride of silver in alkaline chlorides, rendered 

 alkaline by addition of potash, soda, or lime, are readily decomposed by 

 common iron pyrites. 



2. That this effect is not produced if such solution of silver is either acid 

 or neutral. 



3. That when chloride of gold is added to an alkaline argentiferous 

 solution of this nature, such mixed solution is capable of depositing the metals 

 contained in it in the form of coherent alloys upon metallic sulphides generally 

 when presented to them. 



4. That these alloys can also be formed from such solutions by voltaic 

 action. 



As will be seen these results show that, by allowing an alkaline solution 

 of gold and silver contact with iron pyrites (a mineral of most common 



* See Trans. N.Z. Inst., Yol. III., Arts. XL. and XLI. 



