236
10.
POSl'1‘lVE RAYS AND lSO'I‘OPES
number, Z, of the element, except for hydrogen. For example, the
atomic number of neon is 10 and the mass number of its lightest
isotope is 20.
10—13.
The Separation of Isotopes.“——When several isotopes
are mixed together, they cannot be separated by the usual chemical
or physical methods. In several cases, however, methods based
on the small mass difÏerences between the various isotopes in the
mixture have been used with success.
For example, the rate 0fevapomz‘ion of a liquid depends inversely
on
the square
root of the weight of the molecules. This means
that the number of light molecules evaporating each second from a
liquid mixture will be greater than the number of heavy molecules.
Ifthe vapor is continuously removed from above a liquid containing
isotopes, the concentration of the heavier isotope in the liquid
will gradually increase.
In' the electm/ylic 77161‘110d, pointed out in section 10—9, the
mobility of the deuterium ions is less than that of the lighter
hydrogen ions.
With continued passage
of the current, the
residual electrolyte becomes richer in deuterium. It is to be noted
that ratio of the masses of deuterium to
“
hydrogen one
”
is as two
is to one, or one hundred per
cent.
In the case of neon, for exam—
pie, the masses are twenty and twenty-two; the difference is only
ten per
cent.
The rate at which a gas diuser through a porous material
varies inversely as the square root of the mass of the molecules.
By repeated,
“
regenerative
”
circulation of neon for twenty hours
through the walls of clay pipes of special design, G. Hertz
23
was
able to obtain a light fraction containing only one per
cent of neon
twenty—two and a heavy fraction containing only about three per
cent of the lighter gas. Normal neon gas contains approximately
nine parts of neon twenty to one part of neon twenty—two.
The mars spectrogmp/z offers a method for the complete separa—
ration of isotopes but is handicapped by the small amount of
material which can be isolated even with large positive ion cui—rents
and long time of operation. However, sufcient quantities of the
lithium isotopes have been isolated for use in nuclear distintegra—
tion experiments.24 (See chapter 14.)
10.
POSl'1‘lVE RAYS AND lSO'I‘OPES
number, Z, of the element, except for hydrogen. For example, the
atomic number of neon is 10 and the mass number of its lightest
isotope is 20.
10—13.
The Separation of Isotopes.“——When several isotopes
are mixed together, they cannot be separated by the usual chemical
or physical methods. In several cases, however, methods based
on the small mass difÏerences between the various isotopes in the
mixture have been used with success.
For example, the rate 0fevapomz‘ion of a liquid depends inversely
on
the square
root of the weight of the molecules. This means
that the number of light molecules evaporating each second from a
liquid mixture will be greater than the number of heavy molecules.
Ifthe vapor is continuously removed from above a liquid containing
isotopes, the concentration of the heavier isotope in the liquid
will gradually increase.
In' the electm/ylic 77161‘110d, pointed out in section 10—9, the
mobility of the deuterium ions is less than that of the lighter
hydrogen ions.
With continued passage
of the current, the
residual electrolyte becomes richer in deuterium. It is to be noted
that ratio of the masses of deuterium to
“
hydrogen one
”
is as two
is to one, or one hundred per
cent.
In the case of neon, for exam—
pie, the masses are twenty and twenty-two; the difference is only
ten per
cent.
The rate at which a gas diuser through a porous material
varies inversely as the square root of the mass of the molecules.
By repeated,
“
regenerative
”
circulation of neon for twenty hours
through the walls of clay pipes of special design, G. Hertz
23
was
able to obtain a light fraction containing only one per
cent of neon
twenty—two and a heavy fraction containing only about three per
cent of the lighter gas. Normal neon gas contains approximately
nine parts of neon twenty to one part of neon twenty—two.
The mars spectrogmp/z offers a method for the complete separa—
ration of isotopes but is handicapped by the small amount of
material which can be isolated even with large positive ion cui—rents
and long time of operation. However, sufcient quantities of the
lithium isotopes have been isolated for use in nuclear distintegra—
tion experiments.24 (See chapter 14.)