Boltioood — Ionium, a New Radio-active Element. 377 



acid and several grams of rare earths from cerite in the form 

 of chlorides were added to the solution. The earths were then 

 separated by the method already described. The material pre- 

 cipitated from a solution of the earths by treatment with 

 sodium thiosulphate was further purified by repeated precipita- 

 tion with the same reagent, and the material finally obtained 

 weighed only a little over one milligram. This material had 

 an activity several thousand times greater than that of an 

 equal weight of pure uranium. It contained when first pre- 

 pared very appreciable amounts of uranium X, but this sub- 

 stance disintegrated with the time until now at the end of 

 about five months its presence can scarcely be detected. Only 

 a relatively small proportion of the total ionium present is 

 obtained by this process. 



liange of the a Particles from Ionium. 



Dr. L. P. Wheeler of the Sheffield Scientific School and Mr. 

 T. S. Taylor of this Laboratory have both been so kind as to 

 measure for me the range in air of the a particles emitted 

 by ionium. They each used a somewhat modified form of the 

 Bragg apparatus and the measurements were conducted on a 

 small quantity of a very active preparation. Their results, 

 obtained independently, were in excellent agreement and gave 

 a range for the a particles of 2-8 centimeters in air (at 760 mm ' 

 pressure). 



Other Radiations from Ionium. 



The question as to whether ionium emits also a /3 and a j 

 radiation is still an open one, as the preparations which I have 

 are not strong enough or old enough to make it possible as 

 yet to reach a definite conclusion. The indications, however, 

 are in favor of the view that ionium emits 13 rays which are' 

 more readily stopped by matter than the /3 rays from ura- 

 nium X. 



Relative Activity of Ionium in Minerals. 



The results obtained on the determination of the relative 

 activity of the amount of ionium in radio-active equilibrium 

 with uranium and radium in a mineral have already been given in 

 an earlier paper.* It was found that the activity of the ionium 

 is about 0*34 and that the activity of the radium is about 045 ; 

 the activity of the uranium with which they are associated 

 being taken as unity. The ratio of the activity of the ionium 



to the activity of the radium is therefore approximately - J — = 

 * This Journal, xxv, 291, 1908. 



