Intelligence and Miscellaneous Articles. 55$ 



DISCOVERY OF COLUMBITE IN THE ENVIRONS OF LIMOGES. 

 BY M. DAMOUR. 



The specimen of this substance was found in a quarry near Chan- 

 teloube, belonging to M. Alluaud, Sen., collected by M. Mathieu, a 

 mineral dealer of Paris, and confounded with specimens of wolfram, 

 triplite, heterosite and dufrenite, brought from the same place. 



Its colour, hardness and great density, induced M. Damour to 

 think that it did not belong to any of the preceding species ; and a 

 qualitative examination proved that it was almost entirely composed 

 of columbic acid and oxide of iron, with a small quantity of oxide of tin. 

 . This specimen had the form of amorphous nucleus, of the size of 

 a hazel-nut, imbedded in yellowish-white felspar. Superficially it 

 was of a tarnished bluish-black colour, with a shining, smooth fresh 

 fracture The powder was of a grayish-black colour. It scratches 

 glass readily ; its density was found to vary from 7*640 to 7*651. It 

 is infusible by the blowpipe. When reduced to powder and mixed 

 with tartrate of potash and carbonate of soda, it fuses on charcoal, 

 and yields some globules of tin. When fused with borax and phos- 

 phoric salt, it reacts like iron. Acids do not act upon it. 



To analyse this mineral, it was reduced to powder and fused with 

 eight times its weight of bisulphate of potash, and the fused mass 

 when cold was treated with a large quantity of hot water. The 

 oxides of iron and tin were almost entirely dissolved in the liquor : 

 the columbic acid was deposited in the form of a white powder, but 

 still retaining a little oxide of tin and iron. It was digested in hy- 

 drosulphate of ammonia, by which the oxide of iron was converted 

 into an insoluble sulphuret, and the sulphuret of tin remained dis- 

 solved in the sulphurous ammoniacal liquor, which was filtered and 

 saturated with acetic acid, and the sulphuret of tin precipitated was 

 collected. The columbic acid, blackened by the sulphuret of iron, 

 was treated with hydrochloric acid ; by this the iron was dissolved, 

 and the columbic acid after washing was perfectly white ; it was 

 dried, ignited and weighed. 



The liquor separated from the sulphuret of tin was treated with 

 ammonia and its hydrosulphate ; by this all the iron was obtained in 

 the state of sulphuret; the liquor separated from it contained no 

 earthy base whatever. 



The sulphuret of iron was dissolved in aqua regia ; by evaporating 

 the solution and treating the residue with water, a minute quantity 

 of silica was left. The ferruginous liquor was saturated with am- 

 monia, and the quantity of protoxide of iron was inferred from that 

 of the peroxide obtained. 



100 parts of the mineral yielded — 



Columbic acid 82-98 



Oxide of tin 1*21 



Protoxide of iron with a trace of oxide of manganese 14-62 



Silica 0-42 



99-23 



M. Damour observes, that although the columbic acid is reckoned 

 as pure, it may possibly contain a small quantity of the niobic and 



Phil. Mag. S. 3. No. 225. Suppl. Vol. 33. 2 O 



