FreBRuARY 18, 1904] 
NA TORE 
381 
February 11.—‘ On the Compressibilities of Oxygen, 
Hydrogen, Nitrogen, and Carbonic Oxide between One 
Atmosphere and Half an Atmosphere of Pressure, and on 
the Atomic Weights of the Elements Concerned.—Pre- 
liminary Notice.’’ By Lord Rayleigh, O.M., F.R.S. 
The observations now referred to were conducted with an 
apparatus designed upon the same lines as that already de- 
scribed.’ It must suffice to mention that the only im- 
portant modification lay in the fact that the two single 
volumes, which, when employed together, constitute the 
double volume, were used separately and alternately, so as 
to eliminate in each set of measurements any question as to 
what the ratio of these volumes exactly is. It is hoped to 
give a full description of the method when it has been ex- 
tended to the examination of other gases, such as nitrous 
oxide and carbonic anhydride. The temperatures ranged 
from 10°-15°, and care was taken that in each measure- | 
ment the mean temperatures should be almost exactly the 
same for the single and for the double volume. 
The results were reduced much as previously explained, 
and give for the values of B, which, according to Boyle’s 
law, should be unity, 
Oxygen ... Ang ox xe 1-00040 
Hydrogen ass us CG 0-99976 
Nitrogen ... Bog sae a8 +++ 1-00017 
Carbonic oxide 1-00028 
B here denotes the quotient of the value of pv at the half 
atmosphere by the corresponding value at the whole atmo- 
sphere. ‘That it would be less than unity in the case of 
hydrogen, and exceed unity for the other gases, is what 
would be anticipated from their behaviour at higher 
pressures. 
If we measure p in atmospheres, and assume, as has 
usually been done, e.g. by Regnault and Van der Waals, 
that at small pressures the equation of an isothermal is 
pu=PV(1+ap), 
where PV is the value of the product in a state of infinite 
rarefaction, then 
a=2(1—B). 
Probably the chief interest of a knowledge of the coefficient 
a is the application to deduce a correction to the relative 
densities of gases as observed at atmospheric pressure, so 
as to determine what would be the relative densities in a , 
state of great rarefaction, 
is applicable.* 
Taking oxygen as a standard, we see that the small 
correcting factor to be introduced in order to pass from the 
ratio of densities at one atmosphere to that at great rare- 
to which alone Avogadro’s law 
faction is (1+a)/(1+a,), or 1+2 (B,—B), the suffix o re- 
lating to oxygen, that is, as follows :— 
Hydrogen 1-00128 
Nitrogen ou 200 coe 1-00046 
Carbonic oxide ... oO nee 1-00024 
The double of the first number, viz. 2-0026, represents, 
according to Avogadro's law, the volume of hydrogen which 
combines with one volume of oxygen at atomspheric 
pressure to form water. Direct determinations by Scott 
gave 2.00245, and Morley, in his later work, found 2 0027, 
so that there is here a good agreement. 
The following table gives the densities of the various | 
gases, referred to oxygen=16, at atmospheric pressure and 
at very small pressure, as deduced from my own observ- 
ations.* 
(Gast Atmospheric Very small 
pressure. pressure. 
Hydrogen 1-0075 1 0088 
Nitrogen 14 003 14-009 
Carbonic oxide 14:000 14-003 
From the researches of M. Leduc and Prof. Morley, it is 
probable that the above numbers for hydrogen are a little, 
perhaps one thousandth part, too high. 
1 “On the Law of the Pressure of Gases between 75 and 150 Millimetres 
of I Mercury © (Phil. Trans., A, vol cxeviii., pp. 417-39 1902). 
2 ‘The application to oxygen and hydrogen was made in my paper, 
the Relative Densities or Oxygen and Hydr Een) 
I P: 448, 1892; ‘Scientific Papers,” vol i, p. 52 
= Roy, Soc. Proc., vol. liii., p. 134, 1893 ; vol. eae ; Pp» 204, 18973; ‘* Scien- 
tific Papers,” vol. iv., pp. 39, 352. 
NO. 1790, VOL. 69] 
“On | 
"(Roy Soc. Proe., vol. | 
The uncorrected number (14 003) for nitrogen has already 
been given,’ and contrasted with the 14-05 obtained by Stas. 
This question deserves the attention of chemists. _ If 
Avogadro's law be strictly true, it seems impossible that the 
atomic weight of nitrogen can be 14-05. 
From the molecular weight of CO, viz. 28,006, we deduce, 
as the atomic weight of carbon, 12-006. 
It should be mentioned that D. Berthelot* has, 
while, calculated very similar numbers, 
observations of Leduc. 
mean- 
based upon the 
Challenger Society, January 27.—Dr. E. J. Allen in the 
chair.—On behalf of the Marine Biological Association, Dr. 
Allen exhibited a chart showing the positions of freeing 
and recapture of marked plaice in the North Sea, and their 
probable lines of migration.—Dr. Fowler contributed notes 
on the vertical distribution of two Biscayan Chatognatha— 
Sagitta serratodentata, apparently seeking the surface by 
day, but deserting it for deeper water, down to 100 fathoms, 
by night or after rain; Krohnia hamata, represented merely 
by small and immature specimens between 50 and 500 
fathoms, larger specimens occurring only between 500 and 
2000 fathoms; none were captured between the surface and 
50 fathoms. This observation tends to strengthen the theory 
of the continuity of the Subarctic and Subantarctic plankton 
by way of the mesoplankton. 
February 2.—H.G. the Duke of 
Bedford, K.G., president, in the chair.—Mr. R. Lydekker 
read a paper, illustrated by coloured lantern-slides, on the 
subspecies of the giraffe (Giraffa camelopardalis). The 
author enumerated ten subspecies, and pointed out the dis- 
tinguishing characters of each.—A paper was read by 
Messrs. Oldfield Thomas, F.R.S., and Harold Schwann 
which contained an account of a collection of mammals 
from Namaqualand presented to the British Museum by 
Mr., C. D. Rudd. The collection consisted of 160 speci- 
mens, referable to 28 species or subspecies, of which one 
new species and three new subspecies were described in 
the paper.—Mr. F. E. Beddard, F.R.S., read a paper on 
the arteries of the base of the brain in certain mammals, 
based on observations he had made on individuals that had 
died in the society’s menagerie.—Mr. G. A. Boulenger, 
F.R.S., read a paper which contained the descriptions of 
three new species of fishes discovered by the late Mr. J. S. 
Budgett in the Niger.—Mr. Boulenger also described the 
type specimen of the silurid fish, Clarias laeviceps, Gill, 
which had been entrusted to him by the Smithsonian 
Institution. 
Faraday Society, February 2.—Dr. J. W. Swan, F.R.S., 
president, in the chair.—Notes on the welding of 
aluminium: S. O. Cowper-Coles. After referring to 
various machines and processes for welding aluminium, the 
author went on to describe his own process, which requires 
no fiux or solder, and does not necessitate the hammering 
of the joint when in the pasty state, the process being 
Zoological Society, 
| especially suitable for wire, rods, and tubes.—Some appli- 
cations of the theory of electrolysis to the separation of 
metals from one another: M. Hollard. The only principle 
hitherto involved in electrolytic separations has been based 
on the method of successive potentials, each metal deposit- 
ing at the potential proper to that metal. In practice this 
principle has only been applied to metals (copper and silver, 
silver and bismuth, mercury and bismuth) the polarisation 
potentials of which are lower than that of hydrogen. Metals 
having polarisation potentials higher than that of hydrogen 
cannot be separated by gradual increase of the E.M.F., on 
account of the extremely small fraction of the current then 
used to precipitate the metal, hydrogen ions carrying most 
of the current. The author has therefore made use of 
three other applications of the theory of electrolysis, de- 
pending on (1) reduction of the resistance of the bath by 
suppressing the formation of gas at the anode; (2) influence 
of the nature of the kathode ; (3) formation of complex salts. 
—Mr. G. Watson Gray read a short preliminary note de- 
scribing an explosion of some high grade ferro-silicon that 
occurred spontaneously a short time ago at Liverpool. The 
gases evolved on boiling a specimen in distilled water were 
1 Rayleigh and Ramsay, Phd. Trams., A, vol. clxxxvi. 
2 Comptes rendus, 1898. 
» D. 187, 1895. 
