H' at. wt. (natural) 1.007967
at. wt. (H') 1.007822
at. no. 1
m.p. - 259.140C
b.p. - 252.870C
density 0.08988 gm./l
density (liquid) 70.8 gm/i. (-2530C)
density (solid) 7016 gm/i. (-2620C)
valence 1.
Electronic configuration
| K |
L |
M |
N |
O |
P |
Q |
| 1 |
2 |
3 |
4 |
5 |
6 |
7 |
| s |
s p |
s p d |
s p d f |
s p d f |
s p d f |
s p d f |
| 1 |
|
|
|
|
|
|
OSMIUM (Gr. osme, a smelt), Os; at. wt. 190.2; at. no.
76; m.p. 3045+300C; b.p. 50271 1000C; sp. gr. 22.57;
valence 0 to +8, more usually +3, +4, +6, and +8.
Discovered in 1803 by Tennantin the residue left when crude
platinum is dissolved by aqua 'regia. Osmium occurs in
iridosina' and in platinum-bearing river sands of the Urals,
North America, and South America. It is also found in the
nickel-bearing ores of the Sudbury, Ontario region along
with other platinum metals. While the quantity of platinum
metalsin these oresis very small, the large tonnagesofnickel
ores processee make commercial recovery possible. The
metal is lustrous, bluish-white, extreneely hard,'and brirtle
even at high temperatures. It has the highest melting point
and lowest vapor pressure of the platinum group. The metal
is very difficult to fabricate, but the powder can be sintered
in a hydrogen atmosphere at a temperature of 20000C. The
solid metal is not affected by air at room temperature, but
the' pd;wdere"d or spongy metal slowly gives off osmium
tetroxide, which is a powerfal oxidizing agent and has a
strdng smell. The tetroxide is highly toxic, and bqils at 1300C
(760 mm). Concentrations in air as low as l0-~ gm./cu.
meter can cause lung congestion, skin damag?, or eye
damage. The tetroxide has been used to detect fingerprints
and to stain fatty tissue for microscope slides. The metal is
almost entirely used to produce very hatd alloys, with other
metals of the platinum group, for fountain pen tips, instru-
ment pivots, phonograph needles, and electrical contacts.
The price of 99 % pure osmium powder-the form usually
supplied commercially-is about $5/gm. or $300 to$450/troy
ounce, depending on~quantity and supplier. The measured
density of iridium and osmium seem to indicate that osmium
is slightly more dense than iriditim, and osmiumhas generally
been credited with being the heaviest known element.
Calculations of the density from the space lattice, which may
be more reliable for these elements than actual measure-
ments, however, give a density of 22.65 for iridium compared
to 22.61 for osmium. At present, therefore, we know either
iridium or osmium is the heaviest element, but the data do
not allow selection between the two.
© 1999 F. Davies
Delphi O.E.M. Co.
All rights reserved
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