276 OSMIUM 



Intake Levels. Osmium occurs with platinum ores and has not been 

 of biological interest. Osmium tetroxide has been recognized as danger- 

 ous on account of its volatility and production of ocular disturbances, 

 asthmatic condition on inhalation, and dermatitis on skin contact (Os-1). 



Radioassay. The contaminating Os^^^ can be eliminated by decay. 

 The presence of Os^^^ should present no difficulties if a pilot sample of the 

 material administered to the biological system is kept for the decay cor- 

 rections. Also it must be remembered that in beta measurements the 

 self-absorption characteristics of the mixture may change with time. 

 Gamma counting will probably be preferred, provided the sensitivity is 

 adequate for the particular samples. 



Chemistry. Methods are not available for estimation of osmium in 

 biological tissue. The volatility of osmium compounds must be taken 

 into account before the use of any wet- or dry-ashing procedures. Sep- 

 aration of osmium from platinum metals has been accomplished by virtue 

 of the volatility of osmium tetroxide, and procedures have been described 

 for its colorimetric estimation by use of reaction with thiourea (Os-2) . 



Os-1. Fairhall, Lawrence T.: "Industrial Toxicology," The Williams & Wilkins 



Company, Baltimore, 1949. 

 Os-2. Sandell, E. B.: "Colorimetric Determination of Traces of Metals," 2d ed., 



Interscience Publishers, Inc., New York, 1950. 



