It melts with microcosmic salt quite readily in both of the flames, to a clear bead, which appears, if a considerable quantity of columbic acid be present, of a yellow color while hot, but colorless when cold, and does not become clouded if the intermittent flame be applied to it.

With carbonate of soda it fuses with effervescence to a bead which spreads over the charcoal.  Melted with more soda, it becomes absorbed by the charcoal.

It yields, moistened with a solution of nitrate of cobalt, and exposed to the oxidation flame after continued blowing, an infusible mass, presenting while hot a light grey color, but after being cooled that of a light red, similar to the color presented by magnesia under the same circumstances.  But if there be some alkali mixed with it, a fusion at the edges will be manifest, and it will yield by cooling a bluish-black mass.

(e.) 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.