On Gold "Refining ly Chlorine Gas. 159 



for coinage was 334,190 ounces, being at the rate of 24,750 

 ounces per annum, 



The average proportional quantity of silver contained in the 

 gold arriving in Sydney is at present very much greater than 

 that given above, owing to the large amount of silvery gold now 

 being found, especially in the neighbouring colony of Queens- 

 land, and for the year 1868 was not less than 36,000 ounces 

 (£9150), and was probably (including that in the gold shipped 

 direct as bullion by the banks) nearer 42,000 ounces. 



Most of the silver thus naturally present in the gold has 

 hitherto been lost to the colony, owing to the expense in Sydney 

 of the acids, &c, necessary for its extraction by any of the usual 

 methods of refining, which left little, if any, margin of profit on 

 the operation. It therefore seemed desirable that some easy 

 and economical process should be contrived for refining, in 

 Australia, without the aid of costly plant and chemicals. 



Twelve months ago, a paper of mine, describing a new process 

 for refining and toughening gold by means of chlorine gas, was 

 read before the Chemical Society, London, a reprint of which, 

 from that Society's journal, now lies upon the table. 



As since the publication of that paper the method of refining 

 therein proposed has been successfuilv brought into practical 

 operation on a large scale, both here and in New Zealand, and 

 there is a probability that its adoption will, before long, become 

 more general, I lay before the members of this Society a some- 

 what detailed account of the process and some of its more 

 striking results. 



I shall, as far as possible, avoid giving the details of the pre- 

 liminary experiments which lead to the practical application of 

 the process, and which have already been published in the 

 journal of the Chemical Society ; but in order to render myself 

 intelligible, some repetition of what is therein contained will be 

 necessary. 



Most people at all interested in the matter, are aware that the 

 ordinary method of separating silver from natural alloys of that 

 metal and gold is a complicated and expensive process, and 

 that the end is attained by melting the gold with at least 2^- 

 times its own weight of silver, and then again separating by the 

 action of acids] the silver thus added, and also at the same time 

 the small quantity originally contained in the gold, thus leaving 

 as a residue fine gold, assaying from 990 to 993 ; the rationale of 

 the operation being this : If the natural alloy were simply placed 

 in the acid, the very large excess of gold in the alloy would com- 

 pletely protect the silver it contained from the action of the 

 acid ; but if the gold is melted with a large excess of silver, so 

 that the silver greatly preponderates over the gold in the 

 alloy treated, then the acid is able to exert its solvent action not 



