contained in the Bavarian Tantalite. 363 
~~ When the solutions of the alkaline tantalates are rendered acid 
with hydrochloric or sulphuric acid, a pale yellow precipitate is 
produced in them by tincture of galls. An orange-yellow precip- 
itate is formed, under similar circumstances, in solutions of the 
pelopates, and a dark orange-red in those of the niobates. 
errocyanid of potassium produces in solutions of the tanta- 
lates of the alkalies, when they have been rendered slightly acid, 
a yellow precipitate ; in those of the pelopates, a brownish-red ; 
in those of the niobates, a red one. 
When the three acids are fused with bisulphate of potash, they 
dissolve in it. Niobie acid alone solidifies with it to a crystalline 
mass. Water removes sulphate of potash from the fused masses, 
and leaves compounds of sulphuric acid with the metallic acids, 
from which, however, the sulphuric acid can be removed by very 
long treatment with water. 
When hydrochloric or sulphuric acid is added to the solution of 
the niobate of potash or soda, and then a bar of zine immersed 
in it, the separated niobic acid soon assumes a very beautiful pure 
blue color. It gradually becomes dirtier, and finally brown. 
The blue color is produced, in the solutions of the alkaline pelo- 
pates, only on the addition of sulphuric acid; but not even then 
18 a blue color produced in the alkaline tantalates, which, how- 
ever, takes place when the solution of the chlorid of tantalium 
in sulphuric acid is treated with water and zinc. os 
Tantalic acid yields before the blowpipe, with the fluxes, col- 
orless beads, even in the inner flame ; pelopic acid gives with the 
microcosmic salt in the outer flame a colorless, in the inner one a 
brown bead. Niobie acid colors the microcosmic salt in the in- 
her flame of a beautiful blue ; the bead can be easily blown col- 
orless in the outer flame. 
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» This tendency of the three acids to assume different isomeric 
Modifications is connected with the great variability which they 
