260 IRIDIUM 



Intake Levels. Iridium is found associated with platinum and has 

 been of Httle or no biological interest. 



Radioassay. Preparation Ir-192-P will probably be most satisfactory 

 for general use. Ir^^^ offers a shorter half-life, but it should be noted that 

 there is considerable radiocontamination with the longer-lived Ir^^-. 

 Routine beta or gamma counting, with the latter preferred, can be used 

 for both isotopes. 



Chemistry. Chemical methods are available only for such materials as 

 platinum scrap and ores that contain relatively large amounts of iridium. 

 Presumably there would be no losses from biological materials upon con- 

 ventional wet- or dry-ashing. Iridium is apparently similar in chemical 

 behavior to rhodium. 



