12 Proceedings of tJic Royal Socidy of Victoria . 



earthenware vessel ; it is allowed again to settle and the top 

 liquor siphoned off, and, finally, the precipitate is emptied into a 

 filter placed within a large funnel ; after it has drained, the 

 whole is dried in an iron dish, nitre sprinkled over it to help to 

 oxidise the filter-paper, and then heated to burn out the organic 

 matter. 



The dried material is finally smelted down in a clay pot with 

 the addition of borax. The gold thus obtained is almost pure. 

 The slags ar.- melted down with carbonate of soda, carbon, and 

 litharge, and large cupels are made to hold the lead so reduced, 

 which is then cupelled in the usual way. 



In addition to the Plattner process, carried out as before 

 described, a dilute solution of chlorine has also been used, but 

 the extractions obtained were not quite so good as with the 

 original method. 



A trial was also made of the Etard-Black process, the details 

 of which were kindly supplied to me by Mr. Stone, of the Govern- 

 ment Analytical Laboratory. It was found that the quantities 

 specified, viz. : — 1st solution, water, 50 gals. ; sulphuric acid, 

 14: lbs. ; 2nd solution, water, 50 gals. ; salt, 15 lbs. ; permanganate 

 of potash, 6 ozs. — gave too weak a solution to be used witii 

 ordinary roasted ores, but on increasing the amount of perman- 

 ganate to about 24 ozs., and allowing the liquor to percolate slowly 

 thi'ough the ore for 60 hours, 96 per cent, of the gold present 

 was extracted. There does not appear to be any special advantages 

 in the method over a dilute chlorine solution. It might be possible, 

 however, to precipitate the gold on charcoal, and by oxidising the 

 liquor again with permanganate, or other re-agents, it could be 

 used over again. In that case the only waste would be due to 

 the sulphuric acid used in dissolving base metals and the perman- 

 ganate used each time. 



Tests have also been made on the roasted ore with dilute 

 cyanide of potassium solutions with highly satisfactory results, 

 and it appears to me that, with proper handling, almost any 

 roasted ore may be treated successfully with the cyanide solutions, 

 with the further advantage that the silver is also recovered. 

 Should the cyanide prove as effective as chlorine as a solvent for 

 gold in roasted ores, then ehloriiiation will soon be a method of 

 the past. 



