Heated in a glass tube, closed at one end, it melts to a brown mass, vaporizes and sublimates to a white powder upon a cool portion of the tube. Immediately above the assay, yellow crystals are visible; these crystals are colorless after cooling, and the fused mass becomes light yellow-colored and crystalline. Upon platinum foil, in the flame of oxidation, it melts and vaporizes, and becomes light yellow and crystalline after cooling. In the reduction flame it becomes blue, and brown-colored if the heat is increased. Upon charcoal, in the reduction flame, it is absorbed by the charcoal; and, with an increase of the temperature, it is reduced to the metal, which remains as a grey powder after washing off the particles of charcoal. _Borax_ dissolves it, in the oxidation flame, upon platinum wire easily, and in great quantity, to a clear yellow, which becomes colorless while cooling. By the addition of more of the molybdenic acid the bead is dark yellow, or red while hot, and opalescent when cold. In the reduction flame, the color of the bead is changed to brown and transparent. By the addition of more of the acid, it becomes opaque. _Microcosmic Salt_ dissolves it in the oxidation flame, upon platinum wire, to a clear, yellowish-green bead, which becomes colorless after cooling. In the reduction flame the bead is very dark and opaque, but becomes of a bright green after cooling. This is the case likewise upon charcoal. _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.