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 |
|
|
|
|
|
|
IRIDIUM (L. iris, rainbow), Ir; at. wt. 192.2; at. no.77;
m.p. 24100C; b.p. 41300C; sp. gr. 22.42 (170C); valence
3 or 4. Discovered in 1803 by Tennant in the residue left
when crude platinum is dissolved by aqua regia. The name
iridium is appropriate, for its salts are highly colored.
Iridium, a metal of the platinum family, is white, similar to
platinum, but with a slight yellowish cast. It is, very hard and
brittle, making it very hard to machine, form, or work. It
is the most corrosion-resistant metal known, and was used
in making the standard meter bar of Paris, which is a 90%
B-17
platinum-lO % iridium alloy. This meter bar has~since been
replaced as a fundamental unit of length (see under Kryp-
ton). Irridium occurs uncombined in nature with platinum
and other metals of this family in alluvial deposits. It is
recovered as a byproduct from the nickel mining industry.
Iridium has found use in making crucibles and apparatus for
use at high temperatures. It is also used for electrical contacts.
Its principal use is as a hardening agent for platinum. With
osmium, it forms an alloy which is used for tipping pens
and compass bearings. The specific gravity of iridium is only
very slightly lower than that of osmium, which has been
generally credited as being the heaviest known element.
Calculations of the densities of iridium and osmium from
the space lattices give values of 22.65 and 22.61 grns./cu. cm.,
respectively. These values may be more reliable than actual
physical measurements. At present, therefore, we know that
either iridium or osmium is the densest known element, but
the data do not yet allow selection between the two. Iridium
costs about 5160 to 5190/troy ounce.
© 1999 F. Davies
Delphi O.E.M. Co.
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