ALUNITE AS A SOURCE OF POTASH. 



dioxide. Upon acidifying the potash solution a strong odor of sul- 

 phur dioxide was noticed. A little hy- 

 drogen peroxide and nitric acid were 

 added, but considerable sulphur was lost 

 which could have been saved by a suit- 

 able oxidizing agent. 



In commercial practice platinized as- 

 bestos or some other catalytic substance 

 could be introduced into the cooler end 

 of the tube where the temperature is 

 about 400 C. The sulphur dioxide arid 

 oxygen passing over this would be again 

 converted into the trioxide and thus 

 saved. The absence of such impurities 

 as arsenic and chlorine would obviate the 

 necessity of washing the gases before 

 passing them over the catalyzer. 



The determination of sulphur trioxide 

 in the alunite used in these experiments 

 showed 26.88 per cent over and above 

 that necessary to combine with the pot- 

 ash present. Theoretically this should 

 all be evolved on ignition. The mean of 

 two determinations, however, made as 

 outlined above, gave an amount of sul- 

 phur trioxide recovered equal to only 

 23.05 per cent, showing a considerable 

 loss as sulphur dioxide. 



The ignited residue was then analyzed 

 both for potash and sulphur. The re- 

 sults are given below : 



Per cent. 



K 2 O in residue 15. 95 



SO 3 in residue 15.37 



SO 3 in residue over and above that com- 

 bined as K 2 SO 4 1. 83 



Alunite has been used heretofore for 

 the manufacture of potash alum, 1 either 

 by heating to 400 or 500 C. and leach- 

 ing out the alum thus produced, or by 

 ignition at a higher temperature and 

 subsequently treating the ignited residue 

 with sulphuric acid and potassium sul- 

 phate. 



Guyot, M. P., Compt. Rend. Acad. Scl., Paris, 95, pp. 693-694, 1001-1003; Thorp, 

 F. H., Outlines of Ind. Chem., pp. 259-260. 

 [Clr. 70] 



