On the Idenfittj of Columlium and Tantalum. 203- 



An equal u eight of tantalite taken from a specimen, of 

 which the specific gravity of 7*8, yielded, by the same 

 treatment, 



White oxide H grains, 



Oxide of iron 4- 



Oxide manganese 



The white oxides obtained from each of these minerals 

 are p^niaikable for their insolubility in tluJ three common 

 iniiierat aciils, as both Mr. llatchett and M. Ekeberg have 

 obserwd. 



I'l muriatic acid they cannot be said to be absolutely in- 

 s<^)lub)e ; but thty are not sufficiently soluble for the pur- 

 poses oi analysis. 



In nitric acid they are also nearlv, if not perfectly, inso- 

 luble. 



In sulphuric acid, when concentrated and boiling, the 

 oxide of columbium may be dissolved in small quantity, 

 and so also may the oxide obtained from tajUalite. 



The proper solvent, as has been observed by Mr, Hatchett 

 and by M. Ekeberg, is potash ; and as it is not required to 

 he in its caustic state, I employed the crystallized carbonate 

 of potash on account of its purity and uniformity. Of 

 this salt about eight grains seemed requisite to be fused 

 with one of the oxide obtained frjin either of these mi- 

 ccrals to render it soluble in water. 



Soda also combines with the oxide, aiid may be said to 

 dissolve it ; but a far larger proportion of this alkali is ne- 

 cessary, and a larger quantity of water. And although a 

 solution may have been effected that is transparent while 

 hot, it very soon becomes opaque in coolmg, and finally 

 almost the whole of the oxide subsides combined with a 

 portion of the soda in a state nearly insolul)le. 



When a solution of the white oxide, obtained from either 

 of these minerals, has been made, as above, with potasii, 

 the whoW may be precipitated by the addition of an acid, 

 and will not be redissolved by an excess of sulphuric acid, 

 of nitric, of muriatic, succinic, or acetic acids. 



But there is a further agreement in the properties of 

 these two minerals, which appears above all others to es-. 

 tablish their identity ; for though they are both so nearly 

 insoluble by any excess of the mineral acids, yet they are 

 each completely dissolved by oxalic acid, by tartaric acid, 

 or by citric acid ; and the solution of each is subject to the 

 same hmitations; for if the precipitate has been dried, jt i* 

 become intractal)le, and can scarcely be dissolved again till 

 alter a second fusion with potash. 



