334 WHARTOX — PALLADIUM (Pd). [April 7, 



and containing also practically all of the precious metals which the 

 ores carried. 



After further roasting and smelting, the concentrated matte is 

 treated for separation of copper from nickel, which is effected by 

 repeated melting with nitre cake and coke in cupola furnaces. The 

 coke converts the nitre cake into sodium sulphide; when the 

 charge is run out of the furnace and cooled it separates easily into 

 two parts, the bottoms containing practically all the nickel, the tops 

 consisting of sodium sulphide and copper sulphide ; the gold and 

 silver going with the tops, the platinum-group metals going with the 

 bottoms. 



In the refining processes that follow, palladium is obtained as a 

 slime, carrying about a thousand times as much palladium propor- 

 tionally as did the original ore, carrying also the other platinum- 

 group metals, and the gold and silver. 



This palladium-bearing slime is melted and refined in a small 

 reverberatory furnace, from which it is ladled out into cold water, 

 forming shot which are charged into small leaden towers, into the 

 top of which hot dilute sulphuric acid is run. Palladium and the 

 other precious metals being electro-negative to the base metals, a 

 galvanic action now takes place in which nickel, copper and iron 

 dissolve rapidly, leaving palladium in a black mud containing two- 

 per cent, or more of that metal. If this residue still contains much 

 copper, that is mostly eliminated by further treatment with hot sul- 

 phuric acid until the stuff contains about 25 per cent, of palladium,, 

 when it is treated with aqua-regia, thus dissolving all the platinum, 

 palladium and gold. 



From this solution platinum is precipitated by ammonium 

 chloride, the palladium in the filtrate is electrolytically precipi- 

 tated with a platinum anode, appearing as a dull gray metal which 

 is hard and brittle, peeling off easily from the cathode. It is then 

 dried and ignited in a reducing atmosphere, when it takes great 

 brilliancy and becomes very soft and pliable, capable of being 

 worked into any ordinary form. I have, for instance, a remarkably 

 nice teaspoon made of it. 



If air is not completely excluded during ignition the palladium 

 will oxidize on the surface taking most beautiful colorations of 

 pink and green. When prepared as above stated palladium is 

 almost absolutely pure, but for occasional traces of copper and iron. 



I purposely refrain from giving all details of the various stages of 



