238 CHROMIUM 



preferred to an earlier one in which the red cells were dried and ground. 

 In a study of Cr^^ distribution, various preparations of chromic chloride, 

 sodium chromite, sodium chromate, and sodium dichromate were admin- 

 istered to rats in amounts of 50 /xc in 4 to 250 /xg (Cr-5) ; 1 mc Cr^^Cls per 

 100 lb body weight was intravenously injected into sheep. Tissue sam- 

 ples were placed in small metal cups and kept in a frozen state until 

 measured directly with a scintillation counter. The bottom of the metal 

 cup was placed in contact with the metal-enclosed crystal, and under these 

 conditions the measurements were apparently independent of the mass of 

 the sample. In another study, rabbits were given 200 ^c Cr^^ in 2 mg 

 chromium; tissues were digested in 10 per cent NaOH, and bones in con- 

 centrated HNO3 for measurement in a specialized cup-type toroidal 

 gamma counter (Cr-6). Details of red-cell-labeling techniques for red- 

 cell survival studies have been reported (Cr-7). 



Cr-1. Gray, Seymour J., and Kenneth Sterling: Determination of Circulating Red 

 Cell Volume by Radioactive Chromium, Science, 112: 179-180 (1950). 



Cr-2. Mitchell, Avard M., and Seymour J. Gray: The Colorimetric Determination of 

 Trace Amounts of Chromium in Tissue, Document AECU-779, Harvard Medi- 

 cal School, Peter Bent Brigham Hospital, no date. 



Cr-3. Urone, Paul F., and Hanns K. Anders: Determination of Small Amounts of 

 Chromium in Human Blood, Tissues, and Urine, Anal. Chem., 22: 1317-1321 

 (1950). 



Cr-4. Sterling, Kenneth, and Seymour J. Gray: Determination of the Circulating 

 Red Cell \"olume in Man by Radioactive Chromium, J. Clin. Invest., 29 : 

 1614-1619 (1950). 



Cr-5. Visek, W. J., I. B. Whitney, U. S. G. Kuhn III, and C. L. Comar: Metabolism of 

 Cr*' by Animals as Influenced by Chemical State, Proc. Soc. Exptl. Biol. Med., 

 84: 610-615 (1953). 



Cr-6. Kraintz, Leon, and Roy V. Talmage: Distribution of Radioactivity Following 

 Intravenous Administration of Trivalent Chromium 51 in the Rat and Rabbit, 

 Proc. Soc. Exptl. Biol. Med., 81: 490-492 (1952). 



Cr-7. Necheles, T. F., Irwin M. Weinstein, and George V. LeRoy: Radioactive 

 Sodium Chromate for the Study of Survival of Red Blood Cells. I. The Effect 

 of Radioactive Sodium Chromate on Red Cells. II. The Rate of Hemolysis in 

 Certain Hematologic Disorders, J. Lab. Clin. Med., 42 : 358-367, 368-376 (1953). 



