Transformation Products of Radium. 301 



derived from the decomposition of the radium contained in 

 them. 



The amount of radio -tellurium to be extracted from the 

 radioactive minerals will always be proportional to their 

 content of radium, and, in consequence, also to the content 

 of uranium, for the investigations of Boltwood and others 

 have conclusively shown that the amount of radium in radio - 

 active minerals bears a constant ratio to the content of 

 uranium. 



The relative activity of radium and radium F, and also 

 the relative amount present in radioactive minerals can easily 

 be deduced. Let N x be the number of atoms of radium F in 

 one gram of radioactive mineral, and N 2 the corresponding 

 number of radium atoms. Let \ l5 X 2 be the constants of 

 change of radium F and radium respectively. In an old 

 radioactive mineral, the amount of radium and radium F 

 have reached a steady state and the same number of atoms of 

 each break up per second. Thus 



Now radium F is half transformed in *38 years, and radium 

 in about 1200 years. Thus 



Nj -38 



= 3-2x10- 



N 2 1200 



Now it is probable that the atomic weight of radium and 

 radium F are not very different. Consequently the weight 

 of radium F in the mineral is '00032 the weight of radium. 

 Now corresponding to each gram of uranium in a radioactive 

 mineral, there is about one millionth of a gram of radium. 

 Consequently, from a ton of mineral, which has an average 

 content of 50 per cent, of uranium, the amount of radium F 

 present is 0*14 milligram. Assuming that the a particles 

 expelled from radium itself and from radium F produce about 

 the same amount of ionization in the gas, the activity of 

 radium F in the pure state will be 3200 times the activity of 

 pure radium at its minimum activity, or 800 times the activity 

 of radium in radioactive equilibrium. 



Marckwald * has worked up 5 tons of uranium residues, 

 corresponding to 15 tons of the Joachimsthal mineral, in order 

 to extract the radio-tellurium (radium F) from it. Simple 

 but very efficient methods of separation were devised, and 



* Ber. d. D. Chem. Ges. No. 2, p. 591 (1905). 

 Phil. Mag. S. 6. Yol. 10. No. 57. Sept. 1905. Y 



