Brown.] 



232 



[May 18, 



Table Showing the Relative Oxidation of Sulphur in Pyrite and Marcasite 

 by a 3 Per Gent. Solution of KMn 0^ at 22°. 



Mineral. 



Pyrite with 3 per cent, solution 

 KMn04 cold. 



IMarcasite with 3 per cent, solu- 

 tion KMnO^ cold. 



5-HOUR. 



2.81 

 2.28 



2.83 



2.77 



Action of 5 Per Cent. Solution of Potassium Permanganate at 

 Ordinary Temperature. 



In this series, as in the last, the action, as far as pyrite was concerned, 

 was practically complete at the expiration of the first hour, but in the 

 case of the marcasite this point was not reached until probably the end of 

 the second hour, and, in fact, in one case was progressive to the end. 

 But one very great discrepancy is to be noted here in the three-hour col- 

 umn with marcasite. The low result in the next column is explained 

 by caking. 



Table Showing the Relative Oxidation of Sulphur in Pyrite and Marcasite 

 by a 5 Per Gent. Solution of KMn 0^ at 22°. 



This series finishes the experiments at ordinary temperatures. In all of 

 them the action was comparatively slight, not exceeding at most 10 percent, 

 of the contained sulphur in the mineral which would not be sufficient to 

 show any marked difference between the two minerals as bearing on their 

 constitution, if the constitution which seems to be indicated by subse- 

 quent experiments (to be presently described) is the true one. 



The oxidations with potassium permanganate at a temperature of 100^ 

 were conducted by suspending the vessel containing the mineral and so- 

 lution in boiling water. Both stoppered bottles and thin glass flasks 

 closed with perforated corks were used for this series of experiments. 

 The water was kept continually boiling and the bottles or flasks were im- 

 mersed deep enough to cover that portion of them containing the per- 

 manganate. Six or eight oxidations were made at one operation. The 



