RADIUM B { ß y } 26.7 minutes.
RADIUM C { a ß y } 13.5 minutes.
RADIUM D { ß } 15 years.
RADIUM E { ß y } 4.8 days.
RADIUM (Polonium) F { a } 140 days.
Table showing the successive generations of the elements of the
Uranium-radium family, the character of their radiations and
their longevity.
253
the ß-rays emitted by radium are very "soft"—_i.e._ slow and
easily absorbed. The a-ray is in no case available for more than
mere surface application. Hence we see that, contrary to what is
generally believed, radium itself is of little direct therapeutic
value. Nor is the next body in succession—the emanation, for it
gives only a-rays. In fact, to be brief, it is not till we come
to Radium B that ß-rays of a relatively high penetrative quality
are reached; and it is not till we come to Radium C that highly
penetrative y-rays are obtained.
It is around this element, Radium C, that the chief medical
importance of radioactive treatment by this family of radioactive
bodies centres. Not only are ß-rays of Radium C very penetrating,
but the y-rays are perhaps the most energetic rays of the, kind
known. Further in the list there is no very special medical
interest.
Now, how can we get a supply of this valuable element Radium C?
We can obtain it from radium itself. For even if radium has been
deprived of its emanation (which is easily done by heating it or
bringing it into solution) in a few weeks we get back the Radium
C. One thing here we must be clear about. With a given quantity
of Radium only a certain definitely limited amount of Radium C,
or of emanation, or any other of the derived bodies, will be
associated. Why is this? The answer is because the several
successive elements are themselves decaying —_i.e._ changing one
into the other. The atomic per-