Thermodynamic Properties of Fluorochloromethanes and -Ethanes Orthobaric Densities and Critical Constants of Three Fluorochloromethanes and Trifluorotrichloroethane' A . F. BENNING AND R. C. MCHARNESS Kinetic Chemicals, Inc., Wilmington, Del.
K
OUTLIYED in the first paper in this series ( I ) , accurate data on the liquid density of a compound are a necessary prerequisite to the calculation of its thermodynamic properties. This paper covers in detail the results obtained in the measurement of the liquid densities of CHClF2, CHC12F, CClsF, and CC1,F-CClF2. It also includes the data obtained in the determination of the rectilinear diameters and critical constants of the four compounds.
All density measurements were carried out in well-agitated baths so that temperature gradients were reduced to a minimum. The temperatures a t which the floats rose and sank were always within 0.1" C. of each other and in most cases within 0.05" C. The average of the two was taken as the temperature a t which the float and the liquid had the same density. Temperatures above -30" C. were measured with mercury thermometers. Below -30" C. a platinum resistance thermometer was used. The density determinations on all four compounds are shown in Tables I to IV. All temperatures were corrected by checking the thermometers used against a platinum resistance thermometer calibrated by the Yational Bureau of Standards. The float and dilatometer densities were corrected for the expansion of Pyrex glass. The dilatometer densities were also corrected for the weight of material in the vapor space. Equations for the calculation of liquid densities over various portions of the temperature range of '70" to +120" C. mere derived from the experimental density data. These equations and the values calculated from them are shown in Tables I to IV. Other density data reported in the literature are also shown.
Density of Saturated Liquid Saturated liquid density determinations were made on the four compounds over the range from -70" C. to within 11" of their respective critical temperatures, employing or by means of calibrated glass floats which covered the density range of 0.8 to 1.6 grams per cc. by increments of approximately 0.1 gram per cc. Density measurements were also made on CCl3Fbetween -30' and +SO" C. in a calibrated dilatometer having a volume of about 35 cc. Excellent agreement between the two methods was obtained over the range in which they duplicated each other. The compounds used in the density determinations had been purified as previously described (2). The material employed in the measurement of densities in the neighborhood of the critical point was of the highest degree of purity. At lower temperatures the next best material was used. 1
Rectilinear Diameter The rectilinear diameters (R. D.) of the four compounds were determined with the aid of the respective vapor pressure
This paper is the fourth in this series of articles ( f , 2. 3).
PLANTOF KINETICCHEMICALS, INC., WHERE "FREON" REFRIGERANTS ARE MANUFACTURED
814
JUNE, 1940
INDUSTRIAL AND ENGINEERING CHEMISTRY
(a), vapor density (S), and liquid density (Tables I to IV) equations. The saturated vapor (dag) and liquid (d,) densities were calculated for cach compound a t intervals of approximately 28" C. between -70" and f155" C. The averages of these two quantities a t the various temperatures were used to set up an equation for the rectilinear diameter of each compound. I n a few cases observed liquid density figures were used instead of the calculated values. The following supplementary vapor pressure equation, which is valid for pressures between 8 and 30 atmospheres] was used in the CC12F-CC1F2 calculations a t 154.4" C. : loglo p
=
87.3784
-
4195.59
Saturated liquid density determinations have been made on CHCIF2, CHC12F, CC13F, and CC12F-CCIF2 at various temperatures between -70' C. and their respective critical temperatures. Portions of the data thus obtained are represented by equations of the form: d/ = '4
- 31.8277 logla I' + 0.0170516 T
pressure, atmospheres abs.
=
T = " K . = ' C. +273.10
The rectilinear diameters of all four compounds were represented satisfactorily by straight lines, the equations of which are given in Table VI together with the data from which they were derived and the corresponding values calculated from the rectilinear diameter equations. At higher temperatures no values are shown for the rectilinear diameter as calculated from the saturated liquid and vapor densities. In these cases
the saturated vapor densities were beyond the range of the equations of state and were determined with the aid of the observed liquid densities and extrapolated values of the rectilinear diameter. These data were used to fix the position of the saturated vapor density curve in the region near the critical point. The data in Table V were used to plot curves showing the values of the saturated vapor density, saturated liquid density] and rectilinear diameter of each compound a t temperatures up to the critical temperature. These curves are shown in Figure 1. The circles are observed values or values calculated from previously reported equations (2, 3) which fit observed data satisfactorily. The squares are values derived from these primary data or with the aid of the equations for the rectilinear diameter. The dew-point saturated vapor density determinations (8) are also shown in Figure 1 (in circles)] since they constitute an independent check on the data derived from the liquid density determinations and the extrapolated equations for the rectilinear diameter.
TABLE I. LIQUIDDENSITYOF CHClF,
-
d, 1.2849 - 0.003450t - 0.0000073t2(-70' t o +25' C.) d, = 1.2652 - 0.002109t - 0.0000298t?(25' t o 65' C.) Deviation t Calod. d, Obsvd. d, from Calod. a .Grams p e r c c .
c.
-69.0 -33.67 - 4.13 +26.19 26.19 50.23 66.67 79.77 87.31
1.4909 1.3907 1.2990 1.1895 1,1895 l.OS40 0.9920 0.8988 0.8173
1,4882 1,3928 1,2990 1.1895 1.1895 1.0841 0.9921
... ...
-0.0027 - 0.0021 0,0000
0.0000 0.0000 -0.0001 --0.0001
... ...
TABLE 11. LIQUIDDENSITY OF CHCLF d, = 1.4256 - 0.002316t - 0.000002612(-40' t o +70° C.) Obsvd. d, Deviation Obsvd. d, t Calod. d, (This Work) from Calod. (Other Work) Grams p e r cc.
c.
- 28.95
+
0.0 14.88 51.80 90.2 120.6 141.3 157.9 168.0
1.4906 1.4256 1.3906 1.2987 1.1956
1.4907
+0.0002
1:3605
-0:0001 +0.0001
1.2988 1.1893 1.0838 0.9918 0,8965 0.8132
Critical Constants
1.426(ll)
...
-0.0062 ...
...
...
... ...
The critical temperature of each compound was determined by heating the necessary amount of liquid of the
... ...
...
...
DENSITY OF CCLF-CClF, TABLE I V . LIQUID dl
O F CCLF TABLE 111. LIQUIDDENSITY d, = 1.5342 - 0,0022821 - 0.000002312(-40' to d, = 1.6191 - 0.001792t 0.00000642t" (60' t o Obsvd. d, ~ ~ ~ 1 Calcd. d, (This Work) from Calcd. o c . Grams p e r cc.
-
- 29.2
+
0.00 15.0 17.2 18.82
26.10
40.50 48.80 59.26 59.26 92.46 126 68 152.8 170.0 183,4 190.9
-
1,5989 1.5342 1.4995 1.4943 1.4904 1.4731 1,4380 1.4174 1.3909 1.3904 1.2986 1.1891
1.5990 1,5342
...
:
1 4605
...
1.4733 1.4379 1.4173 1.3904 1.3904 1.2986 1,1891 1.0837 0.9917
...
0.8170
...
...
0.8965
+O.OOO1 0.0000
...
+0:0001 +O.0002
- 0.0001 -0.0001 -0,0005
0.0000 0.0000 0.0000
...
... ... ...
+ B t f Ct'
The density data are used i n conjunction with the vapor pressure and vapor density data previously reported (2, 3) to determine the respective rectilinear diameters. The critical temperatures of the four compounds are determined, and their critical pressures and densities evaluated.
where p
815
1.6212- 0.0021721- 0.00000330t~(-30' t o f l 2 0 " C.)
t
+60° C . ) 125' C.) i Obsvd. ~ dlt i (Other Work)
... 1 .4'995(6) 1.4944(10)
... ...
... ...
... ... ... ... ...
... ...
c.
- 30.0
~
~- 29.4
0.0 0.0
0.0 + 20.0 13.96 25.0 25.0
30.0 36.0 40.0 55.52 60.0 80.0 93.15 124.12 154.4 177.2 102.4 203.2 209.3
Calcd. d,
Obsvd. dl (This Work)
~ ~ ~ from Calcd.
i Obsvd. ~ dt, i (Other Work)
Grams per cc. 1,6834 1,6822 1,6212 1.6212 1.6212 1.5902 1,5764 1.5648 1,5648 1,5531 1.5411 1.5290 1.4904 1.4790 1.4263 1.3902 1.3008
... ... ...
... ...
:
1.6878(9)
1 6865
+i):0033
1:i902
0:0000
... ...
.. .. .. ...
... ... ... ... ...
... ...
... ... 0:0000
:. . .
1 4904 1:3902
1.2985 1.1891 1.0836 0.9916 0.8964 0.8169
...
-
1,5?$0(7) 1.5635(8) 1.42 ( 4 ) 1.5521(9) 1,5398(8) 1.5278(7) 1.4282(9) 1.479i(9)
0:0000 0.0023
...
... ... ... ... ...
... ...
... ... ...
...
~
~
816
INDUSTRIAL AND ENGINEERING CHEMISTRY
highest degree of purity in a sealed glass tube until the liquid meniscus disappeared. The temperature was then a l t e r n a t e l y lowered and raised a definite amount until the meniscus appeared and disappeared. T h e true critical temperature was taken as the average of the temperatures a t which the meniscus would just appear and disappear. In no case was t h e r e more than 0.4"C. difference between the two. The critical pressure of each compound was determined by plotting its vapor pressure data (2) as log p us. 1/T and extrapolating the curve thus obtained to the critical temperature. In no case was it necessary t o extrapolate the curve more than 6" C. The critical densities were obtained by extrapolation of the equations for the rectilinear diameter (Table V) to the critical temperature. The critical constants of the four compounds, a s found by the methods described, are given in Table VI. Other values reported in the literature are also shown.
06
OB
10
DENSITY-G./CC
12
1.4
16
VOL. 32, NO. 6
TABLEV. RECTILINEAR DIAMETER OF FLUOROCHLORO HYDROCARBOKS
+
7 -
t
oc.
df
dllo
R. D-.
(daU d f ) 2
Equation
Crams per cc.-
7
CHClFz: R. D. =
= 0.6534
-67.78 -40.00 -12.22 +15.56 43.33 50.23 66.67 79.77 87.31
0.001224 0.004873 0.01418 0.03412 0.07391 0.088 0.137 0.197 0.256
-40.00 -12.22 4-15.56 43.33 71.11 90.2 120.6 141.3 157.9 168.0
d +a, CHClzF: R. D. = 8 1 1= 0,7142 2 0.000499 1.5141 0.7573 0,001981 1.4536 0.7278 0.005774 1.3890 0.6974 0.01371 1.3204 0.6671 0.6381 0.02837 1.2478 0.04441 1.1893 0.6169 0.085 1.0838 ... ... 0.132 0.9918 ... 0,192 0.8965 0.253 0.8132
1,4852 1.4112 1.3260 1.2295 1,1178 1.0840 0,9920 0,8968 0.8173
...
... ... ...
= 0.7682
-34.44 -12.22 +15.56 43.33 71.11 98.89 124.12 154.4 177.2 192,4 203.2 209,3
0.7573 0.7271 0.6974 0.6675 0.6375 0.6170 0.5842 0.5619 0.5440 0.5331
R. D.
-tdi
1.6921 1,6473 1.5866 1.5209 1.4501 1.3742 1.2985 1.1891 1.0836 0.9916 0.8964 0.8169
0.0 -0.1 0.0 +o. 1 -0.1 0.0
...
0.0 0.0 0.0 +O.l +o. 1 +o. 1 -0.2
...
... ...
...
= 0.8106
=
... ...
... ...
0.001083t
... ... ... ...
d
+O. 1 -0.2 -0.1 +o. 1 -0.1
- 0.001078t
0.8111 0.7816 0.7513 0.7208 0.6908 0.6607 0.6322
0.000362 0.001479 0.004417 0.01069 0.02232 0,04225 0.07525 0.122 0.177 0.243 0.306 CCLF-CClFz:
-
%
0.0013371
0.7440 0.7069 0.6697 0.6326 0.5955 0.5862 0.5643 0.5467 0.5367
I . .
-40.00 -12.22 +l5.56 43.33 71.11 98.89 126.67 162.8 170.0 183.4 190.9
-
0,7432 0.7080 0.6701 0.6318 0.5959
CClaF: R. D.
Difference 7
-
0.0010951
0.8461 0.8240 0.7945 0,7637 0.7324 0.7017 0.6747 0,6415
f0.3 0.0 -0.1 -0.1 0.0 to.1 0.0 0.0
...
,..
... ... ...
...
... ,..
TABLE VI. CRITICAL COXSTANTS OF FLUOROCHLORO HYDROCARBONS
--Critical Temp.-----. Compound This work Other work
c.
CHCIFz CHC1zF CClsF CCLF-CClFz
96.0 178.5 198.0 214.1
c.
96.4(6)
.. .
187:6(7)
Critical --Critical PressureDensity, This work Other work This W o r k dtm. Atm. G./cc. 18.7 51.0 43.2 33.7
18.48(5)
... ...
...
0.552 0.522 0.554 0.576
Literature Cited
(1) Benning, A. F., and McHarness, R. C., IND.ENG.CHEST.,31, 912-16 (1939). (2) Ibid., 32, 497 (1940). (3) Ibid., 32, 698 (1940). (4) Booth, H. S., Mong, W. L., and Burchfield, P. E., Ibid., 24, 328-31 (1932). (5) Booth, H. S., and Swinehart, C. F., J . Am. Chem. Soc., 57, 0 1337-42 (1935). (6) Desreux, V., Bull. a m . chim. Belg., 44, 249-87 (1935). (7) Hovorka, F., and Geiger, F. E., J . Am. Chem. Soc., 55, 4759-61 (1933). FIGURE1. ORTHOBARIC DENSITIES (8) Locke, E. G . , Brode, W. R., and Henne, A. L., Ibid., 56, 17268 (1934). OF FLUOROCHLORO HYDROCARBOXS (9) Riedel, L., 2. ges. Kdlte-Ind., 45, 221-5 (19381. (10) Swarts, F., Ber., 26 Ref., 291-2 (1893). From top to bottom: (11) Ibid., 26 Ref., 781-2 (1893). CHClFz, CHCLF, (12) Swarts, F., J . chim. phys., 28, 622-50 (1931).
CClaF, CChFCClF,
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