398 



TABLES 507-510. 

 RADIOACTIVITY. 



TABLE 507. Total Number oi Ions produced by the a, 0. and 7 Rays. 



The total number of ions per second due to the complete absorption in air of the /8 rays due to I 

 gram of radium is 9 Xio 14 , to the y rays, i3Xio 14 . 



The total number of ions due to the a rays from i gram of radium in equilibrium is 2-56XIO 16 . 

 If it be assumed that the ionization is proportional to the energy of the radiation, then the total 

 energy emitted by radium in equilibrium is divided as follows : 92.1 parts to the a, 3.2 to the )8, 47 

 to the 7 rays. (Rutherford, Moseley, Robinson.) 



TABLE 508. Amount of Radium Emanation. Curie. 



At the Radiology Congress in Brussels in 1910, it was decided to call the amount of emanation 

 in equilibrium with i gram of pure radium one Curie. [More convenient units are the millicurie 

 (io~ 3 Curie) and the microcurie (io~ 6 Curie)]. The rate of production of this emanation is 1.24X10 9 

 cu. cm. per second. The volume in equilibrium is 0.59 cu. mm. (760 cm., OC.) assuming the emana- 

 tion mon-atomic. 



The Mache unit is the quantity of Radium emanation without disintegration products which 

 produces a saturation current of io~ 3 unit in a chamber of large dimensions, i curie = 2.5 Xio 9 

 Mache units. 



The amount of the radium emanation in the air varies from place to place ; the amount per cubic 

 centimeter of air expressed in terms of the number of grams of radium with which it would be in 

 equilibrium varies from 24Xio~ 12 to 35oXio- 12 . 



TABLE 509. Vapor Pressure of the Radium Emanation In cms. of Mercury. 



(Rutherford and Ramsay, Phil. Mag. 17, p. 723, 1909, Gray and Ramsay, Trans. 

 Chem. Soc. 95, p. 1073, I 99-) 



Temperature C. 127 101 65 56 10 +17 +49 +73 +100 +104 (crit) 

 Vapor Pressure. 0.9 5 76 100 500 1000 2000 3000 4500 4745 



TABLE 510. - References to Spectra of Radioactive Substances. 



Radium spectrum: Dema^ay, C. R. 131, p. 258, 1900. 



Radium emanation spectrum : Rutherford and Royds, Phil. Mag. 16, p. 313, 1908 ; Watson, Proc. 



Roy. Soc. A 83, p. 50, 1909. 

 Polonium spectrum: Curie and Debierne, Rad. 7, p. 38, 1910, C. R. 150, p. 386, 1910* 



SMITHSONIAN TABLES. 



