On Gold Refining ly Chlorine Gas. 165 



mechanically mixed being eliminated at the same time), it is 

 melted in a boraxed white pot, with the addition of from 8 to 10 

 per cent of metallic silver, rolled to about one-eighth of an inch 

 thickness. The chloride of gold is by this means reduced at the 

 expense of the metallic silver, chloride of silver being formed 

 while the liberated gold sinks and melts into a button at the 

 bottom of the pot. As soon as the whole is thoroughly melted, 

 the pot is removed from the furnace and allowed to stand about 

 ten minutes, and the still liquid chloride of silver is then poured 

 into large iron moulds, so as to form slabs of a convenient thick- 

 ness for the next operation, that is its reduction to the metallic 

 state. 



After the fusion of the chlorides, a small quantity of a curious 

 spongi-form substance adheres to the sides of the crucible used, 

 probably consisting of subchloride of silver ; but, since it always 

 contains a little gold, care has to be taken in pouring off the 

 fluid chlorides, to prevent this auriferous sponge from falling out 

 and mixing with them. 



The fusion of the chlorides with metallic silver does not 

 remove every trace of gold, but with proper care the amount 

 remaining in the silver produced need not exceed three parts in 

 10,000, or about two grains of gold in every lb. troy of silver, a 

 quantity too small to pay for further extraction in this colony. 



The slabs of chloride of silver are reduced without difficulty 

 by plates of wrought iron or zinc in the usual way, but my friend 

 and colleague Dr. Leibius has contrived a very excellent appa- 

 ratus for this purpose, of which he will, I believe, read a 

 description this evening. 



The Manager of the Bank of New South "Wales has kindly 

 allowed me the use of 500 ounces of Queensland gold to illustrate 

 this paper. This quantity was divided into two nearly equal 

 parts, one portion weighing 248 ounces was left in its original 

 unrefined condition as seen in the ingot on the table ; the other 

 portion weighing 252 ounces was refined in the manner described 

 above, and the resulting bar of fine gold assaying 995 is placed 

 by the unrefined ingot for comparison, and the silver extracted 

 weighing 38 - 8 ounces and assaying 991*1 lies beside it. 



Besides the separation and recovery of the silver as above 

 described, another useful end is gained by this process. 



A very large proportion of the gold of Australia, more 

 especially that obtained by amalgamation from our quartz veins, 

 is more or less brittle, an effect generally due to the presence of 

 small quantities of lead or antimony, rendering the bullion quite 

 unfit for coinage or manufacture until it has undergone some 

 process to render it tough. 



The methods usually employed for this purpose are either 

 fusion with nitre and borax, melting with oxide of copper, or the 



