\ ~l 



Polonium, Radium, and Radioactinium. 125 



Summary. 



(1) Methods ol ! separating radium D, radium E, and 

 polonium in the pure state in a form suitable for physical 

 work are described in detail. 



(2) The 7-radiations from polonium, from radium, and 

 from radioactinium have been investigated. Polonium emits 



7-radiation of one type only,having a value of ~\ — 215 (cm.) _1 fc 



This radiation is due to the polonium itself, and is not due to 

 impact of the a-rays of polonium against the metal on which 

 it is deposited. 



The a-rays of polonium are able to excite a soft 7-radiation 

 in copper, though not to an appreciable extent in platinum 

 or in lead. This excited radiation in copper is possibly the 

 characteristic radiation of copper in Series L. 



A very small quantity of /3-radiation is also emitted by 

 polonium. 



(3) Radium itself freed from its products has been found 

 to emit 7-rays. This 7-radiation appears to consist of three 

 types, one of which is much softer than the other two. The 



softest type has a value of ^-(cm.)" 1 in aluminium of about 



130, and the other two types of 6 and 0*1. The intensity of 

 the 7-radiation from radium itself is about 1 to 1J, per cent., 

 of that of radium in equilibrium with its short-lived products.. 



(1) The quantity of polonium separated from two different 

 quantities of old radium of known age was about two to three 

 times smaller than is to be expected if the separation were 

 approximately quantitative and the period of radium D were 

 16*5 years. 



(5) Radioactinium emits two types of 7-rays, the value of 



^r (cm.) _1 in aluminium of one being about 8, and that of the 



other about 0*1. The results given in a previous preliminary 

 communication regarding the existence of a new product in 

 the actinium series are withdrawn. 



We have to express our w r armest thanks to Professor 

 Rutherford for placing at our disposal the apparatus and 

 valuable radioactive material necessary for the carrying out 

 of the work, and for his stimulating interest and advice at 

 all times. 



