most of the radioactive products differ in penetrating power, 
Transformation Products of Radium. 649 
aluminium screens. It is well known that the « rays from 
and the identity of the a rays of radium E and radio-tellurium 
in this respect is a strong indication that the radioactive 
matter is the same in both cases. The agreement of the 
absorption of the rays, together with the similarity of the 
radiations and chemical behaviour, affords very strong 
evidence in favour of the identity of the two products. If 
this is the case the activity of the radio-tellurium must decay 
to half value in about one year. 
It is natural here to consider the question whether the 
product radium E is also identical with the polonium 
discovered by Mme. Curie. Hach acting constituent attaches 
itself to bismuth and emits only a rays. The test of pene- 
trating power of the rays cannot be applied, since the 
polonium, as commercially sold, is usually mixed with bismuth 
and. not, as in the case of Marckwald’s radio-tellurium, 
deposited on a thin film on the surface. The activity observed 
at the surface is thus due to @ rays, which have already 
decreased in penetrating power due to their passage through 
different thicknesses of bismuth. The « rays from polonium 
in consequence appear to be more readily absorbed than those 
from radium H, but it is not unlikely that the difference 
observed may be due entirely to the different experimental 
conditions in the two cases. Mme. Curie states that the 
activity of polonium decays slowly with the time, and mentions 
that one specimen lost half its activity in elevenmonths. The 
rate of decay of activity is about the same as that deduced 
from the product radium H. Mme. Curie, in addition, 
observed that an active product could be separated from 
radium itself by precipitating bismuth added to the radium 
solution. ‘This active matter present with the bismuth could 
be concentrated in exactly the same way as was employed 
for the polonium obtained directly from a solution of pitch- 
blende. Giiesel long ago observed that bismuth was made 
active when placed in a radium solution, and considered that 
polonium was in reality “induced bismuth.” The product 
removed on the bismuth must in both cases have been 
radium EH, so that we have here direct evidence that polonium 
and radium EH exhibit similar chemical properties. 
In the original paper giving an account of the discovery 
of polonium, Mme. Curie states that the active matter could 
be concentrated to some extent by heating the active sulphide 
in a vacuum. The active sulphide was more volatile than 
the bismuth, and was deposited on portions of the glass tube 
between 300° C. and 350°C. On the other hand, I have 
