•g OV THE IDENTii T OF COLUMBIUM A^'D TANTALUM. 



potash retnlcrs The proper solvent, as has been observed ijy Mr. Hatchett 

 it soluble 1" jinj ;\5r. Eckeberg, is jmtash ; and as it is not required to be 

 in its caustic state, I emplo3'ed the crystallized carbonate of 

 potash on account of its puriij' and uniformity. Of this 

 salt about eight grains seemed requisite to be fused with one 

 cf the oxide obtained from either of these minerals to ren- 

 der it soluble in water. 

 Soda doc; not Soda also combines with the oxide, and may be said to 

 except in la^ne dissolve it ; but a far greater proportion of this alkali is ne- 

 with heat.' 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 cooling, and finally al- 

 most the whole of the oxide subsides combined with a por- 

 tion of the soda in a state nearly insoluble. 

 •Precipitated When a solution of the white oxide, obtained from either 



from th; al- of these minerals, has been made, as above, with potash, the 

 yanaci , ^.^^^^ ^^^y ]^^ 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. 

 Stfluble under ^"* there is a farther agreement in the properties of these 

 certain cir- two minerals, which appears above all others, to establish 

 soTev^egel'dble *^^''' identity; for though they are both so nearly insoluble 

 acids. by any excess of the mineral acids, yet they are each com- 



pletely dissolved by oxalic acid, by tartaric acid, or by ci- 

 tric acid ; and the solution of each is subject to the same 

 limitations; for if the precipitate has been dried, it is be- 

 come intractable, and can scarcely be dissolved again till af- 

 ter a second fusion with potash. 



If to the alkaline solution of either of them there be 

 xioa precipi- added infusion of galls, prussiate of potash, or hidrosul- 

 tated b> galls, phuret of potash, no precipitate occurs; but when a suffi- 

 cient quantity of acid has been added to neutralize the re- 

 dundant alkali, the infusion of galls will then occasion an 

 orange precipitate; but prussiate of potash causes no preci- 

 pitate, nor does the hidrosulphuret prec;|)itate the oxide, al- 

 though the solution may become turbid from precipitation 

 of sulphur by a redundant acid. 



The characteristic precipitant of columblum is conse- 

 necessary in quently the infusion of galls; but in the employment of 



the aijplicjtion this test certain precaution* are necessary. For as an ex- 

 •f ihia test. ^ 



