lybdic 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 decompo