ARSENIC 



207 



Arsenic 73 ( 76 days) 

 Arsenic 74 (17.5 days) 



Cat. No. 

 AS-73-74-P 



Mica W. 

 1.7 X 10-2 



S/j. Act. 

 CF 



Int. C. 

 7.1 X 10-" 



Form 

 Chloride 



Beta Gamma 0.052 K 



Beta 0.95, 0.72, 1.40 Gamma 0.59 A' 



Cost Chem. Cont. liadiochem. Cant. 



$75/mc Ge — 



Scint. C. 

 2.3 X 10-1 



Rf/m,c 

 As"', 0.3 

 As'S 3.9 



Intake Levels. Arsenic is of biological interest primarily because of 

 its high toxicity and its use as an insecticide and drug. Food levels of 

 arsenious oxide are usually less than 1.4 ppm, although fish, especially 

 shellfish, may contain up to 170 ppm. The minimum fatal dose for man 

 is about 0.8 to 2.4 mg/kg and for the lower warm-blooded animals, about 

 15 mg/kg; there are considerable species differences. Crop plants range 

 from about 0.1 to 4 ppm on a dry-matter basis. 



Radioassay. As'^^'^'* has perhaps been most widely used and has the 

 advantages of high specific activity and low radiocontamination ; however, 

 it is somewhat more expensive. As^'' has the lower specific activity but a 

 shorter half-life, which may be of advantage for some purposes. As" has 

 both a high specific activity and a short half-hfe, but will require chemical 

 processing to eliminate the germanium radiocontamination. Suitable 

 methods for separation of arsenic and germanium have been described 

 which are based on the fact that arsenic trichloride and germanium tetra- 

 chloride are volatile, whereas arsenic pentachloride is not (As-1). Beta 

 counting may be used for all three isotopes, and also gamma counting for 

 As^^'^^ and As^«. 



Chemistry. The estimation of arsenic in biological materials has 

 received consideral)le attention. The destruction of organic matter must 

 be done carefully to avoid losses. Poor recoveries have been reported 



