90i On the Id<int'Uy of Columhluin and Tajifalum. 



re-agents I have employed are in the hands oF every cbc- 

 mist, the properties which I shall eninDerale are such as 

 will he most useful in the practical examination of any 

 other minerals in which this metal may be found to occur. 



In appearance the columbite is so like tantalite, that it 

 is extremely difficult to discern a difference that can he 

 relied upon. The external surface, as well as the colour 

 and lustre of the fracture, are precisely the same; but co- 

 lumbiie breaks rather more easily by a blow, and the frac- 

 ture of it is less uniform, appearing in some parts irre- 

 gularly shattered ; nevertheless, when the two are rubbed 

 against each other, the hardness appears to be the same, 

 and the colour of the scratch has the same tint of very 

 ilark brown. 



By analysis also, these bodies are found to consist 'of 

 the same three incredieiits; a white oxide, combined with 

 iron and manganese. 



Either of these minerals, when reduced to powder, is very 

 readily acted upon by potash ; but as the iron contained in 

 them is not affected by alkalies, it appeared better to add 

 a small proportion of borax. 



Five grains of columbite being mixed with 25 grains of 

 carbonate of potash and ten grains of borax, were fused 

 together for a few minutes, and found to be perfectly in- 

 corporated. The colour was of a deep green, from the 

 quantity of manganese present. The mass when cold 

 could be softened with water, and a portion of the oxide 

 could be so dissolved; but it seemed preferable to employ 

 dilute muriatic acid, which, by dissolving all other ingre- 

 dients excepting columbium, left the oxide nearly white, 

 by the removal of iron and manganese that had been com- 

 bined with it. 



The muriatic solution having been poured off and neu- 

 tralized with carbonate of ammonia, the iron was then 

 separated by succinate of ammonia ; after which the man- 

 ganese was precipitated by prussiate of potash. 



The products thus obtained from five grains of columbite, 

 after each had been heated to redness, were nearly^ 



White oxide 4 grains 



Oxide of iron ^ 



Oxide of manganese . . . ^ ; 

 but it cannot be supposed that proportions deduced from 

 experiments made on so small a scale can be entirely de- 

 pended upon, although the properties of bodies may be so 

 discerned, nearly as well as when larger quantities are em- 

 ployed. 



All 



