_Niobium_ (Ni).--This metal occurs as niobic acid in columbite
(tantalite). Niobic acid is in its properties similar to columbic
acid. It is white and infusible. By heating it either in the flames of
reduction or oxidation, it presents as long as it continues hot, a
greenish-yellow color, but becomes white when cool. Borax dissolves it
in the oxidation flame quite readily to a clear bead, which, with a
considerable quantity of niobic acid, is yellow when hot, but
transparent and colorless when cold. A saturated bead is clear when
either hot or cold, but becomes opaque when heated intermittingly.

In the flame of reduction, borax is capable of dissolving more of the
niobic acid, so that a bead overcharged and opaque in the oxidation
flame appears quite clear when heated in the flame of reduction. A
bead overcharged in the flame of reduction, appears by cooling dim and
bluish-grey.

Microcosmic salt dissolves in the flame of oxidation a great quantity
of it to a clear bead, which is yellow while hot, but colorless when
cold.

In the flame of reduction, and in presence of a considerable quantity
of niobic acid, the bead appears while hot of a light dirty blue
color, and when cold, of a violet hue; but by the addition of more
niobic acid, the bead, when hot, is of a dirty dark blue color, and
when cold, of a transparent blue. In the presence of the oxides of
iron, the bead is, while hot, of a brownish-red color, but changing
when cool to a dark yellow.

This acid fuses with an equal quantity of carbonate of soda upon
charcoal, to a bead which spreads very quickly, and is then infusible.
When fused with still more soda, it is absorbed.

When moistened with nitrate of cobalt, and heated in the flame of
oxidation, it yields an infusible mass which appears grey when hot,
and dirty green when cold; but if the heat has been too strong, it is
fused a little at the edges, which present a dark bluish-grey color.

_Pelopium_ (Pe).--This metal occurs as an acid in the mineral
columbite (tantalite), and is very similar to the two preceding
metals.

(_f._) _Pelopic Acid_ (PeO^{3}).--This acid is white, and appears
yellow when heated, but resumes its white color when cold. Borax
dissolves it in the oxidation flame to a clear colorless bead, which
appears, when overcharged and heated intermittingly, enamel-white when
cold. This is likewise the case in the flame of reduction, but when
overcharged the color is light grey, when the