Transformation Products of Radium. 303 



doubt that the u ray constituent in polonium is the same 

 as in radio-tellurium, and is identical with the product 

 radium F. " 



The presence of radium D in polonium could be determined 

 by testing if it emitted any rays. From the method of 

 separation of polonium from the mineral, it is not improbable 

 that some radium D would be removed with it. 



Radium I) and Radio-Lead. 



In my previous paper it was suggested that radium D was 

 the primary constituent in the radio-lead separated from pitch- 

 blende by Hofmann. This conclusion has been very strongly 

 confirmed by recent investigations. I have examined a 

 specimen of radio-lead, kindly separated for me by Dr. 

 Boltwood of New Haven. This specimen was four months 

 old at the time of testing. The ray activity has not appreci- 

 ably changed in the course of the following six months, but 

 the a. ray activity has been steadily increasing. This is exactly 

 the result to be expected if it contains radium I). The 

 product radium E would be in radioactive equilibrium at the 

 time of testing, so that the ray activity would remain con- 

 stant. Since radium F is not continuously produced, the 

 a. ray activity should increase with time for several years. 



Hofmann has observed that the activity of the radio-lead 

 prepared by him did not appreciably decay with the time, indi- 

 cating the presence of a slow transformation substance. In some 

 recent experiments, Hofmann, Gonder, and Wolfl"* have made 

 a careful chemical examination of radio-lead, and have shown 

 the presence of two distinct radioactive constituents, which 

 are probably identical with radium E and F. The radioactive 

 measurements were unfortunately not very precise, and the 

 periods of change of the separated products have not been 

 very closely examined. 



Experiments were first made by them on the effect of 

 adding substances to a solution o£ radio-lead and then remov- 

 ing them by precipitation. Small quantities of the platinum 

 metals in the form of chlorides were left in the solution for 

 several weeks, and then precipitated by formalin or hydroxyl- 

 amine. All of these substances after separation were found 

 to give out both a and rays. A large proportion of tht 

 ray activity disappeared in the course of six weeks, and oi 

 the a ray activity in one year. The ray activity is probably 



* Annul d. Phijs. v. p. 615 (1904). 



Y2 



