Carbonate of Soda dissolves it upon platinum wire in the oxidation flame with intumescence, to a clear bead, which appears milk-white after cooling.  Upon charcoal the soda and the molybdic acid are absorbed, the latter is reduced to the metallic state, the metal remaining as a grey powder after washing off the particles of charcoal.  When molybdic acid, or any other oxide of this metal, is exposed upon platinum wire, or with platinum tongs, to the point of the blue flame, a yellowish-green color is communicated to the external flame.  If also any of the compounds of molybdenum are mixed in the form of a powder with concentrated sulphuric acid and alcohol, and the latter inflamed, the flame of the alcohol appears colored green.

(c.) Osmium (Os).—­This metal occurs associated with platinum.  It is of a bluish-grey color, and is very brittle.  Ignited in the open air, it is oxidized to volatile osmic acid, which is possessed of a pungent smell, and affects the eyes.  It communicates a bright white color to the flame of alcohol.  Osmium oxide (OsO^{2}) is converted in the oxidation flame to osmic acid, which is volatilized with a peculiar smell, leaving a sublimate.

In the reduction flame it is reduced to a dark-brown infusible metallic powder.  It produces no reactions with fluxes.  Carbonate of soda reduces it upon charcoal to an infusible metallic powder, which appears, after washing off the particles of charcoal, of a dark-brown color.

ELEVENTH GROUP.—­PLATINUM, PALLADIUM, IRIDIUM, RHODIUM, RUTHENIUM.

These metals are infusible before the blowpipe.  They are not volatile, nor are they oxidizable.  Their oxides are, in both flames, reduced to a metallic and infusible powder.  They give no reactions with fluxes, but are separated in the metallic form.  These metals are generally found associated together in the native platinum, also with traces of copper, lead, and iron.

The metal palladium is found native, associated with iridium and platinum.  This metal generally occurs in greatest quantity in Brazil.

The metal rhodium is found along with platinum, but in very small quantities.

Iridium occurs in nature associated with osmium, gold, and platinum, in the mines of Russia.  Its great hardness has rendered it desirable for the points of gold pens.  In South America this metal is found native, associated with platinum and osmium.  The latter metal, associated with platinum and iridium, has been found in South America.

As these metals will not oxidize or dissolve, they cannot be separated from each other by the blowpipe with the reagents peculiar to that species of analysis.  It is true that colors may be discerned in the beads, but these tints proceed from the presence of small traces of copper, iron, etc.

The ore of osmium and iridium can be decomposed, and the former recognized by its fetid odor.  This metal, strongly ignited in a glass tube with nitrate of potash, is converted to the oxide of osmium, which gives an odor not unlike the chloride of sulphur.