360 On a New Metal, Pelopium, 
does not produce a precipitate in the cold, in the solution obtained 
by boiling and diluted with water, but only on boiling. | Chlorid 
of niobium does not dissolve in cold hydrochloric acid, and scarcely 
anything is dissolved on the addition of water: when, however, 
chlorid of niobium is boiled with hydrochloric acid, though not 
dissolving at first, on diluting with water the whole dissolves, 
and the niobic acid is not even precipitated from the solution by 
boiling. . When sulphuric acid is added, a turbidness results 
even in the cold, and the whole of the niobic acid is pre- 
cipitated by boiling. On the other hand, when but a small 
quantity of hydrochloric acid is placed in contact with the hy- 
drates of the acids, the result is quite a different one. ‘The same 
is the case when the chlorids of the three metals are treated 
with much water. The niobic acid is then completely separated 
on boiling from the chlorid of niobium, and also the pelopic acid 
from the chlorid of pelopium ; but tantalic acid does not separate 
quite so completely from the chlorid of tantalium. 
Chlorid of tantalium, heated with a solution of hydrate: of 
potash, is partly dissolved ; but a solution of carbonate of potash 
does not dissolve any tantalic acid even on boiling. Chlorid of 
pelopium is dissolved in large quantity by a solution of caustic pot- 
ash, and even carbonate of potash dissolves it in tolerable abun- 
dance on boiling. Chlorid of niobium is dissolved even in the 
cold by a solution of potash, and also by boiling in a solution of 
carbonate of potash. 
Tantalic acid remains white on being heated to redness; pe- 
lopic acid is rendered slightly yellowish ; niobic acid, dark yel- 
low. On cooling, both again become as white as before ignition. 
All three acids exhibit, when their hydrates are heated ver) 
strongly, the phenomenon of phosphorescence. This, however, 1S 
not the case when the compounds with sulphuric acid are treated 
with ammonia, and then heated to redness. : 
Tantalic acid, exposed in a current of hydrogen to a strong red 
heat, remains white ; pelopic and niobic acids become black ; but 
the reduction which these acids undergo is quite inconsiderable, 
for very doubtful traces of water are perceptible, and the black- 
ened acids quickly become white when heated with access of 
air, Without experiencing any perceptible increase in weight. 
When tantalic acid is heated to redness in a current of gaseous 
ammonia by a brisk charcoal fire, it is turned gray, with the for- 
mation of but slight traces of water. Pelopic and niobic acids 
become black, and are reduced, with the production of a consid- 
erable quantity of water. 
When tantalic acid is heated in a brisk charcoal fire, and sul- 
phuretted hydrogen gas passed over it, it becomes slightly grays 
but no trace of water is perceptible. Pelopic and miobic acids 
are converted by the same treatment slowly but entirely into SU 
phurets, with formation of water and separation of sulphur. 
