154 Adion of Iodine upon Sulphides. 



night), the results are noted ; the contents of each tube are 

 then heated to boiling, and the results again recorded. The 

 solutions were tested by suitable reagents after expelling by 

 heat the excess of iodine. 



Stibnite, treated in the manner described-, is strongly attack- 

 ed ; and with excess of iodine the solution turns deep brown - 

 red. On boiling the red solution, it loses color as the iodine 

 volatilizes, and after the latter is completely expelled, suitable 

 reagents demonstrate the presence of sulphuric acid and of 

 antimony. The decomposition of this mineral is complete. 

 Molybdenite is not attacked either in the cold or on boiling. 

 Argentite is attacked in the cold, yielding a red solution 

 and a yellowish-white precipitate. If an excess of iodine be 

 present, the mineral is completely decomposed in the cold. 



Galenite is decomposed in the cold, the liquid being com- 

 pletely decolorized. Lustrous, yellow crystals of plumbic 

 iodide form on the surface of the mineral. On heating, the 

 action is increased ; and the solution deposits, on cooling^ 

 large and abundant crystals. 



Sorniteis strongly attacked in the cold, the solution being 

 brown-red and the residue yellowish-white. On heating, the 

 decomposition is hastened, and a heavy precipitate of cuprous 

 iodide forms. 



/Sphalerite is strongly attacked in the cold, the solution 

 turning dark red and a crystalline precipitate forming. On 

 heating, the decomposition is complete. 



Chalcocite is strongly attacked in the cold, the solution with 

 excess of iodine being brown-red. On the application of heat, 

 the action is increased, but little (if any) cuprous iodide 

 forms. 



Cinnabar is feebly attacked in the cold. On heating, it is 

 readily decomposed, with formation of small scarlet crystals, 

 of mercuric iodide. 



Pyrrhotite is strongly attacked in the cold ; the solution is- 

 not completely decolorized, and becomes darker on heating. 

 .Pyrite is decidedly attacked in the cold ; on boiling, the, 



