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The vapour pressure of ethylene
Physica XVI, no 3
Maart
THE VAPOUR PRESSURE
1950
OF ETHYLENE
by A. MICHELS AND T. WASSENAAR 102nd publication of the Van der Waals Fund •Van dec Waals Laboratory, Gemeente-Universiteit, Amsterdam
Summary T h e v a p o u r p r e s s u r e of C2H 4 h a s b e e n m e a s u r e d b e t w e e n - - 1 2 5 ° C a n d + 8 ° C a n d i t is r e p r e s e n t e d as a f u n c t i o n of t e m p e r a t u r e b y a f o r m u l a , containing four constants: l°log P ~ A / T + B I°Iog T + C T + D, whereA=--1243'766,
B=--11"213927,
C=0"01102331,
D~30'470741.
§ 1. Introduction. The vapour pressure of ethylene has been measured between --125°C and +8°C, covering a pressure range from 0.25 to 48 atmospheres. The method and apparatus were essentially the same as those described in a previous paper 1), with the exception that this time the platinum resistance thermometer was placed directly next to the equilibrium cell in the cryostat. The thermometer was calibrated at the triple point of water, the melting point of mercury, the triple point of carbon dioxide and the boiling point of oxygen. In earlier papers the preparation 2) of C2H4 and the method for testing its purity 1) has been described. § 2. Results. The results are given in table I. The logarithm of the pressure is plotted as a function of 1/T in fig. 1. All points lie on a smooth curve. To give a better impression of the experimental accuracy an equation of the form 1°log P = A / T + B 1°log T + C T + D (I) was fitted to the experimental points by the method of least squares. The following values of the constants were obtained : A = - - 1243"766 B . . . . 11"213927
C = + 0"01102331 D = + 30"470741 - -
2 2 1
- -
222
A. MICHELS AND T. W A S S E N A A R
TABLE I
The vapour pressure of ethylene
Pexp. a t m
T°K
Pcatc. atm.
Pexp.--Peatc.
0.25690 0.42477 0.54541 0.70186 0.84771 0.98059 0.98069 0.98078 0.98078 1.02032 1.02032 1.02036 1.19428 1.77476 2.19056 2.72991 3.9058 5.3379 7.5778 10.5481 14.3118 19.0615 22.7850 26.3283 31.0273 35.7569 40.8129 44.3586 46.6873 47.6481
149.367 156.11s 159.74 s 163.601 166.619 169.03 s 169.03 v 169.044 169.041 169.713 169.70, 169.707 172.44 s 179.774 183.968 188.569 196.604 204.23, 213.61 z 223.332 233.10, 243.07 s 249.674 255.269 261.89s 267.842 273.59, 277.305 279.61 v 280.545
0.25613 0.42409 0.54525 0.70238 0.84818 0.98128 0.98116 0.98150 0.98138 1.02114 1.02091 1.02056 1.19547 1.77652 2.19416 2.73294 3.90445 5.3283 7.5635 I0.5320 14.2952 19.0517 22.7768 26.3238 31.0336 35.7709 40.8355 44.3800 46.7078 47.6640
+0.0008 +0.0007 +0.0002 --0.0005 --0.0005 --0.0007 --0.0005 --0.0007 --0.0006 --0.0008 --0.0006 --0.0003 --0.0012 --0.0018 --0.0036 --0.0030 + 0.0014 +0.0096 +0.0143 +O.Ol61 +0.0166 +0.0098 +0.0082 +0.0045 --0.0063 --0.0140 --0.0226 --0.0214 --0.0205 --0.0159
W i t h this formula the pressures were calculated at the experimental temperatures. The differences from the experimental pressures are shown in table I column 4 and are plotted in fig. 2.
§ 3. Comparison with earlier measurements. In the pressure region above a few atmospheres measurements of C r o m m e 1 i n and W a t t s 3) are available. Their results are compared with the present ones in figure 2. B e t w e e n 0 and 1 atm. more data have been published 4)5)e). These have been compared with those given here in figure 3 - - being a part of figure 2 on a larger scale - - b y substituting the various temperatures in formula (1) and plotting the differences b e t w e e n the
THE VAPOUR
PRESSURE
223
OF ETHYLENE
- - I 0
N.'
--
I$ 10
\
--
$
$
--
Fig. 1. The log of the vapour pressureas a function of 1/T. (S) present measurements. [ ] critical point as given by M a a s s and G e d d e s k ) t c = 9.50°C, P c = 49.98 arm.
Z
3$
\_
--C
I
Z73
~
I
200
175
"~-
I
15OAK
%.~-P,:m,. +p o.o+
--
CzH+
/
--
arm
/ O.OZ - -
-O.OZ
/
/
Fig. 2. The difference between experimental and calculated pressures as a function of T. (~) present measurements. / data ofJ C r o m m e l i n and W a t t s a ) .
_4t-..
Fig. 3. Part of figure 2 on a larger scale. (Z) present measurements. / ; data of H e n n i n g and S t o c k 4 ) . /~ data of E g a n and K e m p S ) . [7] d a t a o f L a m b and R o p e r 6 ) .
224
T H E VAPOUR P R E S S U R E OF E T H Y L E N E
calculated and experimental pressures. As the various authors have adopted different values for the position of the ice point on the Kelvin scale, small corrections had to be applied for the temperatures quoted to reduce them to the recommended value of the ice point
(273.15°K). Egan and K e m p S ) claim an absolute accuracy in their temperature measurements of not more than 0"05°C, which corresponds at the boiling point of C2H4 with a pressure uncertainty of 2 mm Hg. Within these limits the agreement is satisfactory. The present measurements give for the value of the normal boiling point tb = - - 103"78°C. After correction for the difference in the values for the ice point the following comparison can be made H e n n i n g and S t o c k 4) __103.74oc (extrapolated) Egan and K e m p S ) __103.72oc Lamb and R o p e r e ) __103.80oc present value 103"78°C The data of E g a n and K e m p agree with the present ones within the accuracy of these authors. -
-
Received 3-12-'49. REFERENCES 1) A. M i c h e l s andT. Wassenaar, Physica 14, 104, 1948. 2) A. M i c h e l s , J. d e G r u y t e r andF. Niesen, Physica 3, 346, 1936. 3) C. A. C r o m m e l i n and H. G. W a t t s , Proc. kon. Ak. Amsterdam, 30, 1057, 1927.
4) 5) 6) 7)
F. H e n n i n g a n d A . S t o c k , Z. Phys. 4 , 2 2 6 , 1921. C . J . E g a n and J. D. K e m p , J. Am. chem. Soc. 59, 1264, 1937. A.B. L a m b andE. R o p e r , J. Am. chem. Soc. 62,806, 1940. O. M a a s s and A. L. G e d d e s , Trans. roy. Soe. (London) A 236, 303, 1937.
ERRATUM THERMODYNAMICAL
FUNCTIONS
OF ARGON
b y A. MICHELS, R. J. L U N B E C K and G. J. W O L K E R S *) Lines 18 to 20 on page 689 should read t
S = S i-RlnO
+f(Cv)p=0T--ldT+
AS i
0
where A S i = (Si, t - + 0 ) t = o = 0.004 t h e s y m b o l S i = Si, o - + p representing the integral
An analogous correction should apply to t h e first formula on page 695 and t h e two lines following. The numerical results of t h e p a p e r are not influenced. *) Physica 15, 689, 1949.
Maart
THE VAPOUR PRESSURE
1950
OF ETHYLENE
by A. MICHELS AND T. WASSENAAR 102nd publication of the Van der Waals Fund •Van dec Waals Laboratory, Gemeente-Universiteit, Amsterdam
Summary T h e v a p o u r p r e s s u r e of C2H 4 h a s b e e n m e a s u r e d b e t w e e n - - 1 2 5 ° C a n d + 8 ° C a n d i t is r e p r e s e n t e d as a f u n c t i o n of t e m p e r a t u r e b y a f o r m u l a , containing four constants: l°log P ~ A / T + B I°Iog T + C T + D, whereA=--1243'766,
B=--11"213927,
C=0"01102331,
D~30'470741.
§ 1. Introduction. The vapour pressure of ethylene has been measured between --125°C and +8°C, covering a pressure range from 0.25 to 48 atmospheres. The method and apparatus were essentially the same as those described in a previous paper 1), with the exception that this time the platinum resistance thermometer was placed directly next to the equilibrium cell in the cryostat. The thermometer was calibrated at the triple point of water, the melting point of mercury, the triple point of carbon dioxide and the boiling point of oxygen. In earlier papers the preparation 2) of C2H4 and the method for testing its purity 1) has been described. § 2. Results. The results are given in table I. The logarithm of the pressure is plotted as a function of 1/T in fig. 1. All points lie on a smooth curve. To give a better impression of the experimental accuracy an equation of the form 1°log P = A / T + B 1°log T + C T + D (I) was fitted to the experimental points by the method of least squares. The following values of the constants were obtained : A = - - 1243"766 B . . . . 11"213927
C = + 0"01102331 D = + 30"470741 - -
2 2 1
- -
222
A. MICHELS AND T. W A S S E N A A R
TABLE I
The vapour pressure of ethylene
Pexp. a t m
T°K
Pcatc. atm.
Pexp.--Peatc.
0.25690 0.42477 0.54541 0.70186 0.84771 0.98059 0.98069 0.98078 0.98078 1.02032 1.02032 1.02036 1.19428 1.77476 2.19056 2.72991 3.9058 5.3379 7.5778 10.5481 14.3118 19.0615 22.7850 26.3283 31.0273 35.7569 40.8129 44.3586 46.6873 47.6481
149.367 156.11s 159.74 s 163.601 166.619 169.03 s 169.03 v 169.044 169.041 169.713 169.70, 169.707 172.44 s 179.774 183.968 188.569 196.604 204.23, 213.61 z 223.332 233.10, 243.07 s 249.674 255.269 261.89s 267.842 273.59, 277.305 279.61 v 280.545
0.25613 0.42409 0.54525 0.70238 0.84818 0.98128 0.98116 0.98150 0.98138 1.02114 1.02091 1.02056 1.19547 1.77652 2.19416 2.73294 3.90445 5.3283 7.5635 I0.5320 14.2952 19.0517 22.7768 26.3238 31.0336 35.7709 40.8355 44.3800 46.7078 47.6640
+0.0008 +0.0007 +0.0002 --0.0005 --0.0005 --0.0007 --0.0005 --0.0007 --0.0006 --0.0008 --0.0006 --0.0003 --0.0012 --0.0018 --0.0036 --0.0030 + 0.0014 +0.0096 +0.0143 +O.Ol61 +0.0166 +0.0098 +0.0082 +0.0045 --0.0063 --0.0140 --0.0226 --0.0214 --0.0205 --0.0159
W i t h this formula the pressures were calculated at the experimental temperatures. The differences from the experimental pressures are shown in table I column 4 and are plotted in fig. 2.
§ 3. Comparison with earlier measurements. In the pressure region above a few atmospheres measurements of C r o m m e 1 i n and W a t t s 3) are available. Their results are compared with the present ones in figure 2. B e t w e e n 0 and 1 atm. more data have been published 4)5)e). These have been compared with those given here in figure 3 - - being a part of figure 2 on a larger scale - - b y substituting the various temperatures in formula (1) and plotting the differences b e t w e e n the
THE VAPOUR
PRESSURE
223
OF ETHYLENE
- - I 0
N.'
--
I$ 10
\
--
$
$
--
Fig. 1. The log of the vapour pressureas a function of 1/T. (S) present measurements. [ ] critical point as given by M a a s s and G e d d e s k ) t c = 9.50°C, P c = 49.98 arm.
Z
3$
\_
--C
I
Z73
~
I
200
175
"~-
I
15OAK
%.~-P,:m,. +p o.o+
--
CzH+
/
--
arm
/ O.OZ - -
-O.OZ
/
/
Fig. 2. The difference between experimental and calculated pressures as a function of T. (~) present measurements. / data ofJ C r o m m e l i n and W a t t s a ) .
_4t-..
Fig. 3. Part of figure 2 on a larger scale. (Z) present measurements. / ; data of H e n n i n g and S t o c k 4 ) . /~ data of E g a n and K e m p S ) . [7] d a t a o f L a m b and R o p e r 6 ) .
224
T H E VAPOUR P R E S S U R E OF E T H Y L E N E
calculated and experimental pressures. As the various authors have adopted different values for the position of the ice point on the Kelvin scale, small corrections had to be applied for the temperatures quoted to reduce them to the recommended value of the ice point
(273.15°K). Egan and K e m p S ) claim an absolute accuracy in their temperature measurements of not more than 0"05°C, which corresponds at the boiling point of C2H4 with a pressure uncertainty of 2 mm Hg. Within these limits the agreement is satisfactory. The present measurements give for the value of the normal boiling point tb = - - 103"78°C. After correction for the difference in the values for the ice point the following comparison can be made H e n n i n g and S t o c k 4) __103.74oc (extrapolated) Egan and K e m p S ) __103.72oc Lamb and R o p e r e ) __103.80oc present value 103"78°C The data of E g a n and K e m p agree with the present ones within the accuracy of these authors. -
-
Received 3-12-'49. REFERENCES 1) A. M i c h e l s andT. Wassenaar, Physica 14, 104, 1948. 2) A. M i c h e l s , J. d e G r u y t e r andF. Niesen, Physica 3, 346, 1936. 3) C. A. C r o m m e l i n and H. G. W a t t s , Proc. kon. Ak. Amsterdam, 30, 1057, 1927.
4) 5) 6) 7)
F. H e n n i n g a n d A . S t o c k , Z. Phys. 4 , 2 2 6 , 1921. C . J . E g a n and J. D. K e m p , J. Am. chem. Soc. 59, 1264, 1937. A.B. L a m b andE. R o p e r , J. Am. chem. Soc. 62,806, 1940. O. M a a s s and A. L. G e d d e s , Trans. roy. Soe. (London) A 236, 303, 1937.
ERRATUM THERMODYNAMICAL
FUNCTIONS
OF ARGON
b y A. MICHELS, R. J. L U N B E C K and G. J. W O L K E R S *) Lines 18 to 20 on page 689 should read t
S = S i-RlnO
+f(Cv)p=0T--ldT+
AS i
0
where A S i = (Si, t - + 0 ) t = o = 0.004 t h e s y m b o l S i = Si, o - + p representing the integral
An analogous correction should apply to t h e first formula on page 695 and t h e two lines following. The numerical results of t h e p a p e r are not influenced. *) Physica 15, 689, 1949.