IX] EXCITED RADIO-ACTIVITY 289 
hikely to throw further light on the processes which give rise to 
the deposit of active matter on electrodes. 
187. Radio-active induction. In carrying out experiments 
on the separation of radium from pitchblende, M. and Mme Curie? 
observed that the separation of the active substance is fairly com- 
plete, if the stage of purification is not far advanced. Copper, 
antimony, and arsenic can be separated practically inactive, but 
other bodies, like lead and iron, always show slight activity. When 
the stage of purification is more advanced, every body separated 
from the active solution exhibits activity. 
Debierne? showed that barium was made active by solution 
with actinium. The active barium removed from the actinium 
still preserved its activity after chemical treatment. In this way 
Debierne obtained barium chloride 6000 times as active as uranium. 
Although the activity of the barium chloride could be concentrated 
in the same way as the activity of radiferous barium chloride, it 
did not show any of the spectroscopic lines of radium. The activity 
however of the barium was not permanent, but decayed to about 
one-third of its value in three months. 
Giesel showed in 1900 that bismuth could be made active by 
placing it im a radium solution, and suggested that polonium was 
in reality bismuth made active by its mixture with the radium in 
pitchblende. Mme Curie also found that bismuth was made active 
by solution with a radium compound, and succeeded in fractionat- 
ing the above bismuth in the same way as polonium. In this way 
bismuth was obtained 2000 times as active as uranium, but the 
activity decreased with time. These experiments are rendered 
very uncertain by the difficulty of completely separating the radium 
from the bismuth. 
Giesel* in 1903 showed that a bismuth plate dipped in a radium 
solution remained active after every care had been taken to remove 
all traces of radium. This active bismuth gave out only a rays, 
and in this respect was analogous to polonium or Marckwald’s 
radio-active tellurium. The absence of the a rays in the bismuth 
indicates that no radium adhered to the bismuth. The activity of 
1 Thesis, Paris, 1903, p. 117. 2 C. R. 131, p. 137, 1900. 
3 Ber. deutsch. Chem. Ges. p. 2368, 1903. 
it, eek 19 
