Analysis of Minerals. 175 



A specimen of Wolframite on analysis by the new 

 method furnished the following result, viz. : — 



W0 3 64-00 



FeO 17-51 



MnO 11*67 



Si0 2 7-20 



100-38 



In this analysis I think the error is due to the silica being 

 too high. 



Quantitative Analysis of Chrome Iroji Ore. 



I have not had time to completely analyse the sample 

 operated upon by the new process, but append the results, 

 as below, the silica and alumina being obtained by difference. 

 I varied the general method in this special instance by 

 adding ammonium nitrate to the solid caustic soda before 

 introducing the same into the silver crucible. This addition 

 of the ammonium nitrate is to cause the chromic oxide 

 liberated to be at once oxydised to chromic acid and com- 

 bined with the excess of caustic soda present, thus forming 

 sodium chromate. The method of working is briefly as 

 follows : — 



The finely divided levigated sample was mixed with ten 

 per cent of its weight (0*5 gram of chrome iron ore was taken) 

 of powdered charcoal and placed into the silver crucible, 

 then five or six times the weight of caustic soda and about 

 three times the weight of the substance taken of ammonium 

 nitrate were placed upon the mineral in the crucible, and the 

 whole heated gently at first, afterwards to redness for 

 half-an-hour or so, over the ordinary Bunsen burner. The 

 cooled mass was afterwards extracted with water, filtered, 

 and the solution evaporated down to dryness in a platinum 

 basin, with ammonium nitrate to separate the alumina and 

 silica, which were then filtered off. The filtrate from this 



