306 



Sulfur 35 (87.1 days) 

 Cat. No. Sp. Act. 



S-35-I 0.3mc/g 



S-35-P-1 CF 



S-35-P-2 

 S-35-P-3 



>10mc/mg 

 >1 mc/mg 



Form 

 Elemental 



H2SO4 



BaS 

 Elemental 



SULFUR 



Cost 



/7.5 mc 



$2/mc 



/mc 

 $5/mc 



Beta 0.166 



Chem. Cont. 

 SOr, NOr 



Ba(0H)2, SO; 



Gamma 



Radiochem. Cont. 

 Possibly P3M14.3 



days) 

 <0.01%P^H14.3 



days) 



S in benzene 



Mica W. 

 4.8 X 10-" 

 Critical Org. 

 Skin 



Int. C. 

 1.4 X 10-4 



Body 

 100 MC 



50% Self-abs. 

 8.2 (detn.) 



Air 



io-« 



Water 

 5 X 10-5 



Effect. Ty, 

 18 days 



Intake Levels. The body contains about 0.15 per cent sulfur, which is 

 present mainly in proteins, and the daily intake for man is approximately 

 1 3 s which, however, must be supphed as particular organic compounds^ 

 A recommended nutrient solution for plants contains about 64 ppm and 

 crop plants range from about 0.1 to 1.5 per cent on a dry-matter basis^ 

 As a result of the high-specific-activity preparations available, there will 

 usually be no problem in keeping the mass of sulfur admimstered at or 

 below physiological levels. 



Radioassay. Any of the processed units is satisfactory. The mam 

 difficulty in counting procedures arises from the soft-beta particles, which 

 are similar in energy to those of C- This -f -/l^at thin-wmdow 

 (<4 mg/cm^) or internal counters must be used and that the ratio ot 

 activity to the mass of sample must be high to avoid undue loss of sensi- 

 tivity An interesting method has been reported for counting liquid sam- 

 ples containing S- in an internal counter using a stainless-steel cup with 

 an airtight cover of aluminum 1.5 mg/cm'^ thick (S-1). The mimmal 

 detectable activity was about 1.5 X lO"'^ ,c; this means that the sensi- 

 tivity was about 0.01 of that of conventional methods. This procedure 

 would be convenient if the loss of sensitivity could be afforded^ 



Chemistry. Sulfur cannot be determined by routine methods of ash- 

 ing, because the organic sulfur may be oxidized and lost. Some of the 

 methods that have been employed for oxidation of biological samples are 

 illustrated in the next section. After conversion of the sidfur m the sam- 

 ple to sulfate, the latter can be estimated chemically and/or prepared for 

 counting by precipitation as barium or benzidine sulfate. Benzidine 

 sulfate has better physical characteristics, but its precipitation requires 

 careful control and cannot be carried out after sodium peroxide fusion 



^^T^pical Methods. Direct Counting. About 1 Mg sulfate as S^Mabeled 

 sodium sulfate containing 15 X 10^ counts/min was intravenously 



