244 Analysis of Chromic Iron Ore. 



2. Before the blowpipe, it dissolves in a bead of borax or mi- 

 crocosmic salt, exhibiting the characteristic reaction of oxide of 

 chrome. 



3. Analysis. — To obtain a proper specimen of the mineral for 

 analysis, it was coarsely broken up and separated from the 

 gangue, as far as practicable. It was then finely pulve.ized, anl 

 one gramme of it ignited with carbonate of soda and caustic po- 

 tassa, in order to convert the oxide of chrome into chromate of 

 potassa. 



4. The fused mass was digested with water and thrown upon 

 a filter, which separated the oxide of iron and that portion of the 

 mineral whi:ch had not been decomposed, from the other constit- 

 uent which passed through in solution. The filter was then 

 treated with hydrochloric acid, which dissolved the iron, leaving 

 the undecomposed ore on the filter. This was found to amount 

 to .353. 



5. The solution of chloride of iron which passed through, was 

 then digested with nitric acid, and the peroxide precipitated by 

 ammonia. This amounted to .172. In a previous experiment, 

 it was found to contain neither alumina nor magnesia, 



6. The solution obtained by the first filtration (4), was next 

 neutralized by nitric acid, enough being added to precipitate and 

 redissolve the alumina. The latter was then precipitated by bi- 

 carbonate of soda and its weight found to be-Jl4i4. 



7. The remaining solution was now evaporated to dryness with 

 carbonate of soda, and treated with water. The magnesia thus 

 rendered insoluble, was separated and amounted to ,090, 



8. In the solution from (7), there still remained the oxide of 

 chrome, which was estimated by concentrating the liquid by 

 evaporation and adding to it while boiling, hydrochloric acid and 

 alcohol. The chromic acid, thus converted into oxide of chrome, 

 was precipitated by ammonia and separated on a filter. The so- 

 lution passing through, still contained a small portion of oxide of 

 chrorne and was therefore evaporated to dryness and digested with 

 water. The oxide of chrome thus rendered insoluble, was added 

 to that before obtained, and the weight of the whole amounted to 

 .244. 



9. Conclusions. — The streak of the mineral being chocolate 

 brown, it is difficult to say whether this color arises from the pro- 

 toxide of iron or the brown oxide of chrome, a problem of exceed- 



