Tables 402-405. 34 1 



RADIOACTIVITY. 



TABLE 402. — Total Number ot Ions produced by the a, ;3. and 7 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 y rays, 13X10'^ 



The total number of ions due to the o 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 the total 

 energy emitted by radium in equilibrium is divided as follows: 92.1 parts to the o, 3.2 to the /3, 47 

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



TABLE 403. — 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 

 (lo^^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., CC.) assuming the emana- 

 tion mon-atomic. 



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

 produces a saturation current of 10-* 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-^^ to 350X10-^2. 



TABLE 404.— Vapor Pressure of tlie Radium Emanation In cms. of Blercury. 



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

 Chem. Soc. 95, p. 1073, i909-) 



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 405. — References to Spectra of Radioactive Substances. 



Radium spectrum : Demar9ay, 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. 



