6 Proceedings of the Royal Society of Victoria. 



In samples Nos. 1, 2, 3 there is a large quantity of iron in the 

 ferrous state ; but in No. 6 there is none, although the oxide is 

 slightly magnetic. Professor Liversidge has noticed this, and 

 called attention to J. Robbin's^ experiment of heating black 

 magnetic oxide until it turns red, when it is found to be still 

 magnetic. 



Many misleading statements'^ have appeared concerning the 

 reactions in roasting furnaces, but it appears that arsenic may be 

 eliminated from any metal so long as sulphur is in excess, and 

 thus there is but little difficulty in roasting any arsenical ores. 

 Antimony ores are more troublesome, since a non-volatile oxide 

 often forms, yet if pyrites is largely in excess the reducing action 

 of the volatilised sulphur tends to prevent highly oxidised forms 

 of antimony forming, and favours the expulsion of antimonious 

 oxide in a volatile form. 



Blende, up to 15 per cent., has not oflered any difficulties, since 

 it is non-volatile and infusible and oxidises mainly to a sulphate, 

 which, if desired, may be leached out. Some is roasted to oxide, 

 and since this is readily acted upon by acids, it may be trans- 

 formed partly into chloride by the addition of salt. The heat 

 should never be raised to such a temperature as to decompc)se 

 zinc sulphate. 



Galena roasts quietly to sulphate of lead ; this, at a high 

 temperature in contact with silica, will evolve sulphuric anhydride 

 and glaze the silica with an impermeable coat of silicate of lead. 

 When present in quantities up to 5 per cent., no trouble was 

 experienced except when roasted with salt, when chloride of lead 

 formed. 



Bismuth oxide passes through the furnace unchanged. 



Copper pyrites. These minerals never amounted to 1 per cent, of 

 the ore put in the furnace, and in small quantities give no 

 trouble ; a mixture of sulphate and oxide remains even after 

 roasting at a high temperature. 



Manganese oxides pass through the furnace and give no trouble ; 

 the cobalt which the earthy ones contain is converted into a 

 sulphate. 



1 Iron rust possessing magnetic properties, A.A.A.S., ISiVi 



2 Wilson's Chlorinate Process. 



