BROMINE 215 



Intake Levels. Bromine has been of interest l)iolo<2;ically in regard to 

 the movement and distribution of bromide ion in hving systems, and 

 particularly on account of the ease of labeling organic compounds and dyes 

 with radiobromine. Foods may contain up to 9 ppm, and about 0.5 ppm 

 in the diet of rats is known to be adequate, although Br is not considered 

 essential. A recommended nutrient solution for plants contains 0.02 ppm, 

 and crop plants range from 1 to 100 ppm on a dry basis. About 875 mg/ 

 kg of sodium bromide ingested daily by rats produced death in 20 days. 

 For rabbits the LDso was 60 to 65 mg/kg of methyl bromide administered 

 in oil. 



Radioassay. The contribution of the K^- impurity can be eliminated 

 by delay in counting samples until the K"*- has decayed to an acceptable 

 level. Routine beta or gamma counting can be used. 



Chemistry. Biological samples may be dry-ashed in the presence of 

 excess KOH or may be wet-ashed in KOH. Bromine may be estimated 

 chemically by oxidation with chromic acid in sulfuric acid and collection 

 of the bromine in potassium iodide solution, after which the liberated 

 iodine can be titrated with thiosulfate. 



Typical Methods. About 1 to 5 mg of Br^'-labeled dibromotrypan blue 

 or dibrom-Evans blue containing 0.07 to 1.2 ^c was injected into mice 

 (Br-1). Approximately 0.5-g tissue samples were treated with 0.5 ml 

 concentrated HNO3 and 0.5 ml of 0.015 M AgNOs in a porcelain ashing 

 capsule; the AgNOs served to reduce volatization of bromine. The res- 

 idue was measured in the capsule with a Geiger counter. In another 

 study, mice were injected with 0.3 to 0.5 mg of a synthetic estrogen con- 

 taining 700 to 2500 counts/min of Br*- (Br-2) ; the tissues were dissolved 

 in 20 per cent KOH, and the solution made to 5 ml and counted directly. 

 In an experiment with eggs about 5 ml of the white was mixed with a Br*^ 

 solution and injected back into the egg, and at the end of the experimental 

 period the egg was frozen in a mixture of ether and dry ice (Br-3). The 

 yolk and white were then separated with a sharp blow and were diluted 

 for solution measurement. Total body chloride in young infants was 

 determined by intravenous administration of 2 mc Br*- per kilogram body 

 weight and measurement of the serum Br*'- and CI after a 24-hr equilibra- 

 tion period (Br-4). Labeled methyl bromide was used to study its behav- 

 ior as a fumigant (Br-5). The counting of AgBr precipitates was fifteen 



