76 APPLIED RADIOACTIVITY 



Sources of Radon 



Radium metal or any of its salts is a source of radon. Radium salts 

 may be obtained commercially as chloride, bromide, nitrate, carbonate, 

 or sulphate. The solubility at 20° C as bromide is 41.4, chloride 19.7, 

 and nitrate 12.2 per cent by weight. Since the radioactive disintegra- 

 tion of radium is independent of its chemical combination and since 

 the radon production depends only upon the actual amount of radium 

 element present, one should refer to the content of a radium container 

 as so many milligrams of radium element. For instance: 



1 gram RaCl2 contains 761 mg Ra element 



1 gram RaCl2-2H20 contains 679 mg Ra element 

 1 gram RaBr2 contains 586 mg Ra element 



1 gram RaBr2-2H20 contains 536 mg Ra element 

 1 gram RaC03 contains 790 mg Ra element 



1 gram RaSC>4 contains 702 mg Ra element 



Definition of Curie 



One curie is defined as the amount of radon in equilibrium with 1 gram 

 of radium. The amount in equilibrium with 1 mg is 1 millicurie (1 mc). 



The number of atoms in 1 curie is 1.71 X 10 16 . 



The volume of radon in equilibrium with 1 gram of radium is 0.65 cu 

 mm (6.5 X 10 -6 gram). 



TABLE 11-13 



Transient Activity of Radon 



Initial increase in beta- and gamma-ray activity in a radon preparation, due to 



accumulation of RaA, RaB, and RaC 



