platinum 音標拼音: [pl'ætnəm] [pl'ætənəm]
n . 白金,鉑
白金,鉑
platinum n 1 :
a heavy precious metallic element ;
grey -
white and resistant to corroding ;
occurs in some nickel and copper ores and is also found native in some deposits [
synonym : {
platinum }, {
Pt },
{
atomic number 78 }]
Platinum \
Plat "
i *
num \,
n . [
NL .,
fr .
Sp .
platina ,
from plata silver ,
LL .
plata a thin plate of metal .
See {
Plate },
and cf .
{
Platina }.] (
Chem .)
A metallic element of atomic number 78 ,
one of the noble metals ,
classed with silver and gold as a precious metal ,
occurring native or alloyed with other metals and also as the platinum arsenide (
sperrylite ).
It is a heavy tin -
white metal which is ductile and malleable ,
but very infusible (
melting point 1772 [
deg ]
C ),
and characterized by its resistance to strong chemical reagents .
It is used for crucibles in laboratory operations ,
as a catalyst ,
in jewelry ,
for stills for sulphuric acid ,
rarely for coin ,
and in the form of foil and wire for many purposes .
Specific gravity 21 .
5 .
Atomic weight 195 .
1 .
Symbol Pt .
Formerly called {
platina }.
[
1913 Webster PJC ]
{
Platinum black } (
Chem .),
a soft ,
dull black powder ,
consisting of finely divided metallic platinum obtained by reduction and precipitation from its solutions .
It absorbs oxygen to a high degree ,
and is employed as an oxidizer .
{
Platinum lamp } (
Elec .),
a kind of incandescent lamp of which the luminous medium is platinum .
See under {
Incandescent }.
{
Platinum metals } (
Chem .),
the group of metallic elements which in their chemical and physical properties resemble platinum .
These consist of the light platinum group ,
viz .,
rhodium ,
ruthenium ,
and palladium ,
whose specific gravities are about 12 ;
and the heavy platinum group ,
viz .,
osmium ,
iridium ,
and platinum ,
whose specific gravities are over 21 .
{
Platinum sponge } (
Chem .),
metallic platinum in a gray ,
porous ,
spongy form ,
obtained by reducing the double chloride of platinum and ammonium .
It absorbs oxygen ,
hydrogen ,
and certain other gases ,
to a high degree ,
and is employed as an agent in oxidizing .
[
1913 Webster ]
platinum Symbol :
Pt Atomic number :
78 Atomic weight :
195 .
078 Attractive greyish -
white metal .
When pure ,
it is malleable and ductile .
Does not oxidize in air ,
insoluble in hydrochloric and nitric acid .
Corroded by halogens ,
cyanides ,
sulphur and alkalis . {
Hydrogen }
and {
oxygen }
react explosively in the presence of platinum .
There are six stable isotopes and three radioisotopes ,
the most stable being Pt -
193 with a half -
life of 60 years .
Platinum is used in jewelry ,
laboratory equipment ,
electrical contacts ,
dentistry ,
and anti -
pollution devices in cars .
PtCl2 (
NH3 )
2 is used to treat some forms of cancer .
Platinum -{
cobalt }
alloys have magnetic properties .
It is also used in the definition of the Standard Hydrogen Electrode .
Discovered by Antonio de Ulloa in South America in 1735 .
The name comes from the Spanish word platina which means silver .
Platinum metal is generally not a health concern due to its unreactivity ,
however platinum compounds should be considered highly toxic .
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