398 



Tables 607-510. 

 RADIOACTIVITY. 



TABLIi 607. —Total Nomber of Ions produced by the a, 0, and y Rays. 



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

 gram of radium is 9 Xio^'*, to the 7 rays, 13X10^*. 



The total number of ions due to the a rays from i gram of radium in equilibrium is 2.56X10'^ 

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

 energy emitted by radium in equilibrium is divided as follows: 92.1 parts to the o, 3.2 to the fi, 47 

 to the y rays. (Rutherford, Moscley, Robinson.) 



TABLE 608.— Amount ol 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~''Curie) and the microcurie (io~ Curie)]. The rate of production of this emanation is 1.24X10"^ 

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

 tion mon-atomic. 



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

 produces a saturation current of IC"^ unit in a chamber of large dimensions, i curie = 2.5X10^ 

 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 24X10-^2 to 35oXio-i2_ 



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, '9°9-) 



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: Demar9ay, C. R. 131, p. 25S, 1900. 



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



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

 Polonium spectrum : Curie and Debierne, Rad. 7, p. 38, 1910, C. R. 150, p. 386, 191G 



Smithsonian Tables. 



