148 

not previously anticipated ; but further experiments 
are required to confirm the result obtained before 
drawing the important conclusions it appears to 
warrant. 
It is hoped to repeat this experiment and others at 
Spitsbergen in the future; but it is desirable that 
other workers more favourably situated should also 
carry out similar experiments extending over a 
longer period. 
The actual outlay of expenses for the experiment 
in 1921 was borne by the Marine Biological Associa- 
tion, and in 1922 by a Government Grant from the 
Royal Society, but in both years essential help was 
provided by the Scottish Spitsbergen Syndicate and 
its scientific leader, Mr. J. Mathieson, 
J. H. Orton. 
Marine Biological Laboratory, Plymouth, 
December 15. 

Separation of Mercury into Isotopes in a Steel 
Apparatus. 
By 305 hours of repeated fractional vaporisation 
from a steel trough in a vacuum at low pressures we 
have obtained a difference of o-1 unit in the atomic 
weight of mercury without other cooling than that 
given by ice. The trough holds 190 c.c. of mercury, 
but another larger apparatus has been constructed in | 
which the capacity is 1o kilos. In this the mercury 

bee ee 
ie 

i 


Fic. 1.—Steel apparatus for the separation of mercury into isotopes 
by vaporisation. A, Cylinder for ice; B, circular condensing 
roof, made of steel; CC, drain for the light fraction, made of 
steel; DD, annular steel trough holding 190 c.c. of mercury ; 
£, watch glass with hole in centre, supported on a short glass 
tube e; #¥, heating element made of calorised wire and 
supported on glass rods; G, collecting tube made of glass; 44, 
ground joint ; 77, mercury seal; A’A, platinum wites ; //, ground 
joint and sealing wax. 
is heated by an insulated wire which lies in the bottom 
of the trough, the insulation being obtained by a 
coating of magnesium oxide, which is covered with a 
steel sheath. This wire is produced by the General 
Electric Company. 
The details of the apparatus are exhibited in Fig. 1. 
By means of the tube G the sample may be divided 
into as many fractions as is desired. In the newer 
form of apparatus the wires used as leads to the 
heating coil pass through insulators in the bottom 
NO. 2779, VOL. I11] 
NATURE 
‘These drops do not fall back into the trough of 



[FEBRUARY 3, 1923 : 
steel plate, and not through the upper part of the 
tube G. The principle of the apparatus is that the 
lighter molecules, which vaporise more rapidly, strike 
the slanting roof above D, and collect in drops. 













mercury, but roll down the slanting ceiling until they 
reach its edge, when they drop into the inverted cone 
in the lower steel plate, and then into the glass tube 
G, which has a capillary of 800 mm. length at the 
lower end. 
The progress of the separation was followed by the — 
use of Fig. 2, due to Mulliken and Harkins, andit was 
Fraction of Material in Diffusates 
90°01 02 03 04 05 06 07 08 09 
[SS 
Se: 
pa 
Change in Molecular Weight (AM) 

10 09 08 07 06 05 04 03 02 Ql 
Fraction of Initia! Material Left in Residue ot Any Time 
Fic. 2.—Generalised diagram showing atomic or molec- 
ular weight of fractions obtained during a 10@ per 
cent. efficient diffusion or irreversible evaporation 
of a mixture of isotopes. 
found that the efficiency of the process is quite 
constant and equal to about eighty per cent. It may 
be stated that Dr. Mulliken is also separating the 
isotopes of mercury in this laboratory, using the 
method of evaporative diffusion, which has an 
extremely high efficiency. His results will be reported 
separately. Our own work will be described more 
fully later, in the Journal of the American Chemical 
Society. WILLIAM D. HARKINS, 
S. L. Maporsky. 
The University of Chicago, 
December 22. 

The Rule of Priority in Nomenclature. 
As a teacher of paleontology and keeper of pala- 
ontological collections, I may perhaps be permitted 
to bring forward for discussion some trenchant points 
which seem to call for immediate action. 
The rule of priority was originally intended to be 
a help in clearing away obscurity in nomenclature, 
but it is now seen that the strict observance of thi: 
rule is having a reverse effect. 
