Isopycnals of liquid helium. II

Physics. -
Isopycnals of liquid helium. 11. By W . H. KEESOM and Miss
A. P . KEESOM. (Comm. N°. 224e from tbe KAMERLINGH ONNES
Laboratory at Leiden).
(Communicated at the meeting of June 24, 1933) .
Summary. M~asurements on the isopycnals of liquid helium were continued to 35 atmospheres. Part of the solidifkation curve could be determined more accurately . The position
of the À-point in this curve was found to be: T = 1.753 0 K. p = 29 . 91 atm. Undercooling
of liquid helium I was observed.
§ I. Introduction. In a former paper 1) we communicated a number of
measurements on isopycnals of liquid belium up to 25 atm. We now
bave continued tbose measurements up to 35 atm.. especially in the
neighbourbood of tbe solidification curve and the upper part of the
L..curve.
We tried to mak~ measurements witb tbe same apparatus also in the
solid state. Tbis appeared. bowever. not to be possible. the measurements becoming irregular, probably in consequence of boles being formed
in the solid matter. In one case we happened to obtain tbe metastable
production of a liquid belium isopycnal into tbe solid belium range.
In other cases wben cooling tbe liquid belium (tbe pressure being
sufficiently bigb) solidilication sbarply set in at a definite temperature.
So we were able to determine part of tbe solidification curve more
accurately than could be done in tbe measurements dealt with in Comm.
No. 184b 2).
For tbe method and for details we refer to Comm. No. 224d.
§ 2. The results bave been collected in tahles land 11 and are represented in Fig. 1.
An isopycnal such as No. XII consists of 3 parts. belonging to liquid
belium I. to liquid belium 11. and to a mixture of liquid helium 11 and
solid helium respectively. tbe latter part coinciding witb the solidification
curve. lsopycnal XI is very cbaracteristic. tbe part belonging to liquid
helium 11 baving become very sbort.The inserted figure on a larger
scale shows tbis part more clearly.
The points marked A of isopycnal IX correspond to supercooled
liquid helium I (cf. § 1).
I) These Proceedings 36. 482, 1933. Comm. Leiden No. 22<fd.
2) These Proc:eedings 35. 794. 1926. Comm. Leiden No. 184b.
613
TABLE I.
Isopycnals of liquid helium. Measurements of May 10, 1933.
I
IX
(!=0.1817 gr/cm 3
T oK
(!
T oK
p atm.
p atm.
I1
1
X
= 0.1760 gr/cm 3
T oK
I
p atm.
I
2.519
31.70
1.143
26.12 2)
2.501
26.78
2.306
34.04
1.359
25.78 2)
2.301
26.20
1.178
25.29 2)
2.108
25.58
1.861
25.23
25.99
33.27
2.082
1.890
32.83
1.352
25.62 2)
1.843
32.72 1)
1. 531
26.712)
1.790
1.780
32 .631)
1.593
27.25 2)
I. 715
1.717
32.63 1)
1.698
28.70 2)
1.694
1.708
28.89 2)
1.724
29 . 24 2)
1.639
27.75
1.635
27.762)
1.904
32.83
1.595
27.32 2)
1.590
27.25 2)
2.09-t
33.32
1. 511
26.60 2)
1.543
26.84 2)
2.501
31.66
1.358
25.83 2)
1.477
26.28 2)
1.116
25.27 2)
26.67
I
27 . 20
I
1
I)
Undercooled liquid.
Solidification curve.
2)
HE
JO
SOLI
----- 1-
p
t
20
~------~----~~-------~~------~______~______~__~
1.0 -
T
1.5
20
2.5
3.0
3.5
~O·I\ .
Fig. l.
39*
614
TABLE 11.
I
Isopycnals of Iiquid helium. Measurements of May 18, 1933.
XI
XII
XIII
(>=0.1793 gr/cm 3
(> = 0.1780 gr/cm 3
(> = 0.1733 gr/cm 3
TOK
I
I
2 . 509
p atm.
I
T oK
I
1.891
31.33
27.83
1
2.301
30.73
2.080
30.02
1.890
I
4.233
1
27.77
1.8H
1
T oK
p atm.
p atm.
31. 20
1
3.504
1
27.47
1
1.809
27 .75
2.987
25.18
29.60
1.792
27 . 85
2.498
23.31
1. 778
29.55
1.770
28.15
2.297
22.83
I. 758
29.58
I.?il
28.68
2 .087
22.25
I. ?i6
29 .76
I. 717
29.10
1.984
22.05
I. 738
29 .671)
1.696
28.87 1)
1.89 1
22 05
1.710
29.08 1)
1.670
28.32 1)
1.858
22.54
1.621
27.64 1)
1. 608
28.48 1)
1.819
23.00
1. 705
28.92 1)
1.980
27 .92
1.778
23.42
1.739
29. 67 1)
2.096
28.20
1.689
24 .32
1.774
29 . 55
2.293
28.85
1.595
24.95
1.894
29 . 59
2.503
29.50
1.486
25.52
2 . 280
30 . 55
2.987
31.48
1.3H
25.?i 1)
2.502
31.35
3.197
33 . 92
1.157
25.29 1)
4.233
37.75
~ Solidification curve.
I
11
Table III gives data for the solidification curve read from the diagram.
TABLE 111.
--
T OK
I
I
IJ
atm.
I
II
T oK
p atm.
I
1.15
25 . 25
1. 50
26 . 19
I. 20
25.34
1.60
27.38
1.30
25.55
I. 70
28.87
1.40
25 .90
I. 75
29.86
615
A remarkable point is that for densities and temperatures at which
the helium was partly solid partly liquid. the solidification curve was
accurately foIlowed with rising as weIl as with faIling temperature. for
so far as the solid-liquid helium 11 part of the curve was concerned.
This was. however. not the case for the solid-liquid helium I part of the
curve. At faIling temperature we decidedly observed an undercooling of
the liquid 1). as already mentioned. whereas at rising temperature equilibrium very slowly was established and sometimes no definite point was
reached.
Using isopycnal XI we could fix the point L' where the À-curve
meets the melting curve. i. e. the À-point in the solidification curve. lts
position is:
T= 1.753° K. p
= 29.91
atm.
Even at 1.18° K isopycnal IX. for which the density was highest.
does not leave the solidification curve to enter the solid region. We
conclude that at 1.18° K the density of solid helium exceeds 0. 1817 gr/cm 3 •
As from the diagram of isopycnals we derive that the density of liquid
helium 11 is 0.1725 gr/cm 3 • we conclude that the difference in density
between solid helium and liquid helium 11 at 1.18° K surpasses 0.0092
gr/cm 3 • From this follows that the melting heat at that temperature
surpasses 0.016 cal/gr. How much these values are surpassed. cannot be
derived from these measurements.
1) Undercooling or the reverse when passing the ..-curve was never observed.
CORRIGENDUM.
Proc. Academy Amsterdam Vol. 36 p. 486 Fig. 2: in stead of Kg/cm 2
read atm.
PhysicS. - Spaltung der natuerlichsten Peldgleichungen fuer SemiVektoren in Spinor-Gleichungen vom DIRAC'schen Typus. Von
A. EINSTEIN und W. MAYER.
(Communicated at the meeting of June 24. 1933).
In einer frueheren Mitteilung 1) haben wir gezeigt. dass die aIlgemeinsten
Semivektor-Gleichungen einfachster Art sich in eine kanonische Form
bringen lassen. in welcher nur drei wiIlkuerliche Konstante auftreten.
Es zeigte sich ferner. dass die DE BROGLIE-WeIle eines solchen Systems
sich in zwei WeIl en typen von Spinor-Charakter aufspalten laesst. welche
sich zwanglos als dem Elektron bezw. Proton zugehoerig deuten lassen.
1) Akademie der Wissenschaften. Amsterdam 1933.