11—13. SEPARATION OF RADIOACTIVE SUBSTANCES 253
.
<———ALPHA RAY
BETA RAY—)
'W
m…… 92
ThC”
Thoriu
ŒË . |. .
Series
Tn
_
-
. .
.
|
’äë %“
ACC”
|.
Actiniu
ACA
An
Series
AcX
.
C
I
Uranium
RaB —È RaC'
Radium
RaARn
Series
'
.
Ra
il
Il
'
_ UI
FIG. 11—6.
Positions of radioactive substances in the periodic‘table.
column of the table are isotopes and, when once mixed together,
cannot be completely separated by any chemical or physical means
known today.
11—13.
The Separation of Radioactive Substances—Substances may be isolated chemically by precipitation, electrochemi,
cal deposition or by fractional crystallization. They may also be
separated by volatilization, Since different substances have dif—_
ferent volatilization points, or by electrolysis. The method of
remi] makes use- of the fact that as an alpha particle leaves its
'
atom the remainder of the substance recoils backwards.
ThuS,
if thorium C, radiùm A or actinium C be placed between positive
and negative,metâl plates, the recoil thorium D, radium B or
—
'
actinium D will collect onthe negative plate. KFrom considerations
,
'
of the momenta invdved,“the velocity of the alpha particle may be
-_
_
COmputéd.
.,
F romfradiùfn A‘,— th1s amounts to 3.16 X 107 cm.
second.
Gases may
be ;freed from_their parents by bubbling ”air
through a solution containing them,
by_ boiling the solution.
‘
In the ignition m'eth'od'for radium’ emanation from radium, the
"
radium salt is mixed With an appropriate ux, such as“ sodium
acid phosphate, and sealed
in a glass tube.
‘
Within 7.7days, 75 _