(Jippsland Aai-lferous Ores. 3 



keep pyrites in excess of arsenical ores, and largely in excess of 

 antimony sulphides ; blanket sand, containing a large amount of 

 silica, serves to dilute the concentrated pyrites. 



The mixture should be dried before introducing it into the 

 furnace, otherwise it will be difficult to screen; and if damp lumps 

 of ore pass in, these will be difficult to roast, since they do not 

 break up and thus pass through the furnace unaltered. By screen- 

 ing through a sieve, containing 4 holes per linear inch, all scraps 

 of iron, lumps of semi-oxidised ore and other injurious materials 

 are eliminated, and the fine material is run through a hopper and 

 spread out upon the floor in a layer about 4 inches deep. Since 

 a perfect oxidising roast is needed, it follows that to perform this 

 operation quickly, a copious supply of warm air is needed, and 

 reducing gases should be excluded. On the other hand, if the 

 upper end of the furnace containing the raw sulphides becomes 

 too hot, these burn and generate a large amount of heat ; if this 

 action is not moderated, fusion cannot be pi'evented, and the 

 sulphides are rendered practically unfit for subsequent treatment. 

 If the temperature is rising too rapidly the air must be shut off, 

 (>r raw blanket sand fed in until conditions are normal. 



Fi'ee sulphur, sulphides of arsenic, and metallic arsenic sublime 

 and pass into a current of air about 2 inches above the surface of 

 the ore, where they burn with a characteristic livid flame, while 

 underneath may be seen a conspicuous, wavy, ])rick-red flame, 

 which I assume to be due to the colour of the volatilised sulphur 

 and sulphides of arsenic. As soon as these reactions go on freely 

 the ore is mobile, and when stirred will run like a liquid, since 

 the various particles are buoyed up on a cushion of sublimed 

 products. 



The ore is stirred vigorously at this stage, and after all 

 sublimation products have disappeared, it is moved on to the 

 next hearth. 



Opposite the second door the flame is emitted from the surface 

 of the ore itself, yet the mass will scintillate brightly, if stirred ; 

 the rabbling is carried on at this stage as continuously as possible, 

 since a large percentage of sulphur is eliminated by oxidation. 



The same material, when moved to the next door, will only 

 sparkle when dropped thi'ough a layer of hot air, and if left 

 unstirred for any length of time a soft crust forms, which 



lA 



