Gippsland Auriferous Or<:n. 5 



slowly acted on by chlorine at a temperature of 800° C, while 

 above that temperature it is more sensibly acted upon, and also 

 at an increasing rate down to 300° C. 



By continually attending to the furnace, ic was found that 

 the raw ore could be shifted from each hearth every 45 minutes, 

 so that pyrites could be perfectly roasted in 4^ hours ; and, 

 generally speaking, a better roast may be obtained in that time 

 than by keeping the ore longer in the furnace. 



In order to find out the state of the ore on the various hearths, 

 samples were taken just before the material was moved down- 

 wards. Unfortunately, samples opposite doors 4 and 5 were 

 mislaid ; but, on testing the others with an ordinary horseshoe 

 magnet, it was found that the material was highly magnetic from 

 No. 1 door down to No. 3. Nearly all works^ on roasting of 

 ores state that pyrites loses one atom of sulphur, and the oxidation 

 of the i-emaining atom is through the agency of sulphuric 

 anhydride uniting with ferrous oxide to form a sulphate, which is 

 afterwards decomposed into ferric oxide and sulphuric anhydride. 

 Such, however, has not been the case in our furnace ; in it, after 

 the distillation of the free sulphur and arsenic products, the 

 material left consists of magnetic sulphide; after contact with the 

 air it becomes magnetic oxide of iron, and finally, by heating in 

 the air alone, it is transformed into the sesqui-oxide. 



The quantity of magnetic material in samples taken from 

 No. 1 floor, 20 % ; No. 2 floor, 24 % ; No. 3 floor, 22-4 %, which 

 contained only 5 % sulphur ; No. 6 floor, -4 %, with no sulphur 

 and no ferrous oxide. The quantity of sulphate of iron present 

 at any stage was exceedingly minute, and, since the heat required 

 for its decomposition was not reached before about the fifth 

 hearth, it is plain that too much stress has been laid on 

 Plattner's statement. 



My present investigations show that very little sulphur is 

 combined with the iron beyond the third floor of the furnace, 

 and in order to more definitely establish what the inain reactions 

 are, samples are being collected from furnaces of various design 

 for future testing. 



1 Roberts-Austin's Presidential Address to Chemical Section British Association, 1891 ; 

 Peter's Jlodern American Methods of Copper Smelting, p. 170 ; Metallurgy of Gold, from 

 Plattner's Metallurgische Rostprozesse, p. 231.-1. K. Rose ; The Metallurgy of Gold.— 

 Eissler, 4th edition, p. 207. 



