The Washington herald. [volume] (Washington, D.C.) 1906-1939, 1922-01-15
SAYS Chemist, ~
ELEMENTS ARE
NOTELEMENTARY
Chicago Professor Finds
Chlorine Atoms Have
Different Weights.
SUNDAY. JANUARY H. Iszz.

SUNDAY, JANUARY II. lszz.
The first successful experiment.
in splitting sp a chemical element
into two weighabie portions which
have different properties have beer
reported by Prof. william d. Hsr-
kins. Of the department OF chem
istry of. the University Of Chicago.
-what we have considered ele-
ments are not actually eiernentsry."
says Prof. Harkins. For more thar
. hundred years it has been cor
sidered that all OF the atoms OF
single element are exactly slIks
II is now found that most eiemenf
consist OF two or more-ususliy no
more than seven-diferent kinds on
atoms. Each OF the species or xmas
Of atoms which make up q single
element is called an 'isotope,' which
means that it acts exactly like all
of the other species Of atoms which
constitute the same element.
Thus lead, considered to be an
element. In found 70 consist Of iso-
TOPICS which act almost exactly like
ordinary lead. and are only spprs-
Gladly different in that their atoms
are heavier or lighter than the sv-
ersge weight OF an atom Of ordi-
nary lead. That lead consists OF
isotopes whose atoms weigh 206.
| 2os, 2lO. 2ia, and 2it. was FIRST
recognized by an English chemist.
soddy. nearly ten years ago. and
this was confirmed by the great
American chemist Richards. who
made extremely accurate determi-
nations Of the atomic weights OF
some of these isotopes.
while IL was thus considered
that the very heavy elements-such
as lead and radium-sre mixtures.
attempts 20 separate such elements
into their different isotopes all
proved failures"
About 1919 Sir J. J. Thomson
found accidentally by using what is
known as the positive ray method,
that the light element neon, one
Of the very rare gases in the at
mosphere, consists Of two kinds OF
J .sotopes, OF atomic weight 20 and
| %, but he did not seem TO feel
| himself that this was definitely
/ proved. In 1915. when Prof. Har-
kins first decided to attempt 20 sep
/ arate an element into parts, he
II decided that the best element for
this purpose was chlorine. another
1 light element. II happens that this
Il element Ereenish. yellow gas
is now best known by the fact that
il was the first poison gas used in
warfare by the Germans.
] Prof Hsrkins had developed the
= rule that any element which con-
sisted Of only one kind OF atoms
would have an atomic weight equal
almost exactly to q whole number.
and this is now known as the
1 whole number rule" Chlorine. OF
all the light elements. had an
atomic weight fsrthest from a
whole number. and this seemed 10
indicate that IL contained large
percentages Of at least two differ
/ ent isotopes, which are more ele-
mentary than the element So
called What is called the ordinary
| or\chemical atomic weight is simply
| the average weight OF all OF the
atoms in an element in terms OF
hydrogen. which is the lightest or
all elements. The atomic weight OF
hydrogen was formerly taken as
equal exactly to unity, but was
later set at a number l.oo7s, which
is only o.7s per cent greater than
unity. This difference has a re-
msrksble Significance, which will
be mentioned later.
Experiments were begun in 1915
and would have proved successful
much earlier than was actually the
case IL they had not been inter
rupted by the war. However, in
January. 1920. Harkins and Broeker~
had separated about third OF an
ounce OF chlorine which has an
atomic weight different from that
OF chlorine. and this separation has
since been repeated and confirmed
by Harkins and Hayes. This is the
first definite separation OF an cle-
ment into parts which has ever
I been demonstrated.
Though the elements are almost
all mixtures, the percentage OF the
mixture has thus far been found to
be the same no matter where the
element Is found upon the surfRce
Of the earth" says Prof. Harkins.
TO explain this fact the English
physicist, Aston. advances the~
hypothesis that these elements have
been thoroughly mixed In the sea.
However. that this cannot be the
true explanation is seen when IL is
considered that the element nickel.
consisting OF two isotopes OF atomic
weight IS and so, has the same
average or chemical stomic weight
in the metecrites (5s.ss) az q has
on earth. or the mixture has just
the same composition in both. as
found by the American chemist,
Baxter. This indicates either thst
the material OF the earth and that
of the meteorites must at one time
have been very thoroughly mixed
together. or that these are just the
proportions in which the atoms
were formed when they were built
up from hydroEen