(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.
(f.) Pelopic Acid (PeO3).—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 bead is cooled.
Microcosmic salt dissolves it in the flame of oxidation, to a clear yellow bead, which loses its color when cold. In the reduction flame, when the bead is highly saturated, a violet-brown color is produced. In presence of the oxides of iron, the reactions are like those of niobic acid. With carbonate of soda, the reactions are similar to those of niobic acid. By heating with nitrate of cobalt, it yields a light grey infusible mass.
(g.) Titanium (Ti).—This metal occurs occasionally in the slags of iron works, in the metallic state, as small cubical crystals of a red color. It is a very hard metal, and very infusible. Titanic acid occurs in nature crystallized in anatase, arkansite, brookite, and rutile. Titanium is harder than agate, entirely infusible, and loses only a little of its lustre, which can be regained by fusion with borax. It does not melt with carbonate of soda, borax, or microcosmic salt, and is insoluble in every acid except the hydrofluoric. By ignition with saltpetre it is converted into titanic acid, which combines with the potassium, forming the titanate of potassium.