64 MUTATION AND PLANT BREEDING 



is given in Table 3. These isotopes emit alpha, beta, or gamma rays, 

 or a combination of two or more. 



It is imperative that carefnl dosage measurements be made if 

 reproducible results are to be obtained in radiation experiments. 

 Generally dosimetry should be done by someone well qualified to 



Table 3. — Radioisotopes Used in Biological Studies, Listed According to Half-life, 

 with Radiations Emitted and, for Some Isotopes, Dose Rate per Curie at 1 Meter. 



Dose rate at 

 Radioisotope Half-life* Radiation (s) 1 meter, r/hr 



emitted per curie f 



Manganese-56 2.56 h 0, y 



Potassium-42 12.7 h 0, y 



Sodium-24 15.00 h 0, y 1.93 



Radon 3.82 d a 



Iodine-131 8.05 d 0, y 0.231 



Phosphorus-32 14.3 d 



Rubidium-86 18.6 d (3, y 



Iron-59 45.1 d 13, y 0.65 



Strontium-89 53 d 



Sulfur-35 87.1 d 



Polonium-210 138.3 d a, y 



Calcium 45 164 d 13 



Zinc-65 245 d 0+, y 0.30 



Cobalt-60 5.27 y 0, y 1.32 



Barium-133 7.2 y y 



Hydrogen-3 (tritium) 12.46 y 



Strontium-90 28 y 



Cesium-137— barium-137 30 y 0, 7 0.356 



Radium-226 , 1,622 y a, 7 0.84 



Carbon-14 5,568 y 



Uranium-238 4.4xl0 9 y a 



*h = hour; d = day; y = year. 



tThese values taken from Kinsman (82, page 139). 



handle the appropriate apparatus. There are many pitfalls for the 

 unwary, and, especially so, with internally deposited isotopes. A good 

 idea of the complexities involved can be obtained from the book by 

 Hine and Brownell (72). The details of dosimetry measurements are 

 not appropriate to this article, but suffice it to say that the amount 

 of radioactivity is determined by counting the number of particles 

 emitted in a given time and that it is commonly designated in curies, 

 millicuries, or microcuries. A curie (abbreviation: c) is defined as 



