of Columbium and Tantalum. 
251 
tate may be made to appear by neutralizing the redundant 
acid ; and for this purpose carbonate of ammonia should be 
employed : for although pure ammonia has no power of dis- 
solving the oxide alone, yet the gallat seemed to be perfectly 
re-dissolved by that alkali. 
When infusion of galls is poured upon the white oxide re- 
cently precipitated, and still moist, it combines readily and 
forms the orange-coloured compound. 
Prussiate of potash occasioned no change in an oxide that 
had been purified by a second fusion with potash ; but it ap- 
peared to dissolve a small portion of the oxide, as infusion of 
galls, poured into the clear liquor, occasioned a cloudy pre- 
cipitate of an orange colour, though no such precipitate took 
place when the infusion was mixed with the same prussiate 
alone. 
Hydrosulphuret of potash being added to the oxide, and 
heated upon it, impaired the whiteness of its appearance, and 
seemed to detect the remains of some impurity which had not 
yet been removed by other means ; but no appearance indi- 
cated the formation of a sulphuret of columbium. 
From a careful repetition of these experiments upon each 
of the oxides, I see no reason to doubt of their perfect agree- 
ment in all their chemical properties ; but there is nevertheless 
a very remarkable difference in the specific gravities of the 
two minerals from which they are extracted. 
The specific gravity of columbite was ascertained by Mr. 
Hatchett to be 5,918 ; that of tantalite was found by M. 
Ekeberg to be 7,953, and I have every reason to suppose 
their results correct, since a small fragment of the former 
appeared upon trial to be 5,87, while a specimen of tantalite, 
