250 HAFNIUM 



Hafnium 181 (45 days) Beta 0.405 Gamma 0.0807 0.480 



Cat. No. Sp. Act. Form Cost Chem. Cont. Radiochem. Cont. 



Hf-181-I 60mc/g Hf02 $G4/48 mc — — 



Rf/mc 

 4 



Intake Levels. Little is known of the distribution or toxicity of 

 hafnium compounds. The LD50 for 10 days in rats for hafnium sodium 

 mandelate administered intravenously was 75 to 100 mg/kg as Hf (Hf-1). 

 When given intraperitoneally daily, the LD50 was 2 to 3 g/kg. These 

 values are similar to those for zirconium. 



Radioassay. Hafnium 181 can be counted by routine beta or gamma 

 methods, and there are no particular problems. 



Chemistry. The chemistry of hafnium is similar to that of zirconium, 

 and the difficulty of separating the two elements has hampered its study. 

 Biological samples may be wet-ashed. 



Typical Methods. Hf^^^Oo was used to prepare hafnium sodium man- 

 delate (Hf-1). One-half milliliter of solution containing 3.06 mg of the 

 metal (about 180 mc) was injected intravenously into the rat. Tissues 

 were weighed and dissolved in concentrated HN0,3, and 10-ml samples 

 counted with a thin-mica-window tube. Feces were homogenized by 

 incubation with a concentrated papain solution to give an aliquot for 

 counting. Filter paper on which urine was collected was digested with 

 H2SO4 to give an aliquot for counting. It was found that erroneous 

 results were obtained when fat was present in the counting solutions and 

 that it was necessary to prepare a one-phase counting liquid by use of 

 dioxane or acetone (Hf-2). 



Hf-1. Kittle, C. Frederick, E. Richard King, Carl T. Bahner, and Marshall Brucer: 

 Distribution and Excretion of Radioactive Hafnium ^*' Sodium Mandelate in 

 the Rat, Proc. Soc. Exptl. Biol. Med., 76: 278-282 (1951). 



Hf-2. Bahner, Carl T., D. B. Zilversmit, and Etta McDonald: The Preparation of 

 Wet Ashed Tissues for Liquid Counting, Science, 115: 597-598 (1952). 



