Brown.] 



234 



[May 1«, 



Action of 1 Per Cent. Potassium Permanganate Solution at 100°. 



The results of the oxidation shown in this series are chiefly remarkable as 

 still further illustraliug the action of the solution on the caked material, 

 as shown in the four- and five-hour trials with pyrite and the four-hour 

 trial with marcasite. This latter shows, too, the effect of having the 

 caked mineral massed in one spot. With this exception, the marcasite 

 oxidations are progressive and fairly uniform (the two hour trial falls 

 somewhat below what it doubtless should be), but the pyrite shows a 

 sharp fall in the four- and five-hour trials. The cause of this has been 

 indicated. That the concentration of the solution by evaporation caused 

 an increase in the action seems to be indicated by the result of the five- 

 hour marcasite oxidation, but this is much more strongly marked in the 

 5 per cent, series in the case of pyrite, which will be referred to later on. 



Table Shoicing the Relative Oxidation of Sulphur in Pyrite and Marcasite 

 by a 1 Per Cent. Solution of KMnOi at 100^. 



Action of 3 Per Cent. Solution op Potassium Permanganate 



at lOOO C. 



The average results of this series of oxidations were very good, with the 

 exception of two members of the series — the marcasite five-hour trial and 

 the pyrite three-hour. This latter was repeated, but with a similar low 

 result. Leaving these two out of account, the average results show a 

 very fairly even rate of progression, which have been brought out in the 

 diagram (PL xvii). It is evident from an inspection of the following table 

 that the marcasite oxidations of the four- and five-hour trials were arrested 

 by some disturbing influence. 



Table Showing the Relative Oxidation of Sulphur in Pyrite and Marcasite 

 by a 3 Per Cent. Solution of KMn 0^ at 100° C. 



