iridium 音标拼音: [ɪr'ɪdiəm]
n . 铱
铱
iridium n 1 :
a heavy brittle metallic element of the platinum group ;
used in alloys ;
occurs in natural alloys with platinum or osmium [
synonym : {
iridium }, {
Ir }, {
atomic number 77 }]
iridium \
i *
rid "
i *
um \ ([-
i ]*
r [
i ^]
d "[
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m ),
n . [
NL .,
fr .
L .
iris ,
iridis ,
the rainbow .
So called from the iridescence of some of its solutions .
See {
Iris }.] (
Chem .)
A rare metallic element of atomic number 77 ,
of the same group as platinum ,
which it much resembles ,
being silver -
white and indifferent to most corrosive agents ,
but harder ,
more brittle ,
and with a higher melting temperature (
2410 [
deg ]
C ,
versus platinum 1772 [
deg ]
C ).
With the exception of osmium ,
it is the heaviest substance known ,
its specific gravity being 22 .
4 .
Symbol Ir .
Atomic weight 192 .
22 .
[
1913 Webster PJC ]
Note :
Iridium usually occurs as a native alloy with osmium (
iridosmine or osmiridium ),
which may occur alone or with platinum .
Iridium ,
as an alloy with platinum ,
is used in bushing the vents of heavy ordnance .
It is also used for the points of gold pens ,
and in a finely powdered condition (
iridium black ),
for painting porcelain black .
[
1913 Webster ]
iridium Symbol :
Ir Atomic number :
77 Atomic weight :
192 .
217 Very hard and brittle ,
silvery metallic transition element .
It has a yellowish cast to it .
Salts of iridium are highly colored .
It is the most corrosion resistant metal known ,
not attacked by any acid ,
but is attacked by molten salts .
There are two natural isotopes of iridium ,
and 4 radioisotopes ,
the most stable being Ir -
192 with a half -
life of 73 .
83 days .
Ir -
192 decays into {
platinum },
while the other radioisotopes decay into {
osmium }.
Iridium is used in high temperature apparatus ,
electrical contacts ,
and as a hardening agent for platinum .
Discovered in 1803 by Smithson Tennant in England .
The name comes from the Greek word iris ,
which means rainbow .
Iridium metal is generally non -
toxic due to its relative unreactivity ,
but iridium compounds should be considered highly toxic .
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