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iridium

more about iridium

iridium


  3  definitions  found 
 
  From  Webster's  Revised  Unabridged  Dictionary  (1913)  [web1913]: 
 
  Iridium  \I*rid"i*um\,  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  the  same  group  as  platinum,  which 
  it  much  resembles,  being  silver-white,  but  harder,  and 
  brittle,  and  indifferent  to  most  corrosive  agents.  With  the 
  exception  of  osmium,  it  is  the  heaviest  substance  known  its 
  specific  gravity  being  22.4.  Symbol  Ir  Atomic  weight  192.5. 
 
  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. 
 
  From  WordNet  r  1.6  [wn]: 
 
  iridium 
  n  :  a  heavy  brittle  metallic  element  of  the  platinum  group  used 
  in  alloys;  occurs  in  natural  alloys  with  platinum  or 
  osmium  [syn:  {Ir},  {atomic  number  77}] 
 
  From  Elements  database  20001107  [elements]: 
 
  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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