Thermodynamic Properties of Fluorochloromethanes and -Ethanes P- V-T Relations of Three Fluorochloromethanes and Trifluorotrichloroethane' A. F. BENNING AND R. C. MCHARNESS Kinetic Chemicals, Inc., Wilmington, Del. while a determination was being H E e v a l u a t i o n of t h e The P - V - T relations of CHClF2, CHC12F, made and to heat it rapidly from thermodynamic properties CCl,F, and CCl2F-CC1F2 have been deterone temperature to the next. A of a compound requires a n water jacket was welded on the mined by the measurement of isometrics accurate knowledge of the presoutside of the bath to facilitate at various pressures between 3.5 and 21 rapid cooling. sure-volume-temperature relaThe remaining ap aratus shown atmospheres. The results are expressed i n tions of its vapor. The methods in Figure 1 was useffor the quanused to acquire this information an equation of state of the Beattie-Bridgetitative introduction of material and the results obtained for the into vapor density bulb G and its man type and used to calculate tables of subsequent removal from the bulb four compounds under investithermodynamic properties for each comin several individual portions. I t gation were outlined briefly in consisted of a chromium-plated pound. ildditional vapor density measurethe first paper of this series ( 2 ) . supply cylinder, K , a valve, L, a ments have also been made a t pressures of McLeod gage, a liquid air trap, This paper covers in detail the 0, and a vacuum pump. All conprocedures followed and the data 0.23 to 2.5 atmospheres and at saturation nections between valves F and L obtained in this study. pressures above 20 atmospheres. were made with l/a-inch (6.25The compounds used in this mm.) copper tubing. The remaining connections were made work had been purified by rewith '/,-inch rubber pressure tubing. peated fractionation as described in the preceding paper (3). Pressure gages A and B were checked against a dead-weight The data obtained have been used to evaluate the constants gage tester for approximate accuracy before being attached to the of an equation of state of the Beattie-Bridgeman type (1). apparatus. Since the expansion and contraction of the oil and mercury in U-leg D affected their readings, the two gages were This type of equation was selected because i t fits the expericalibrated in place after the vapor density determinations had mental values satisfactorily over the entire pressure range been made on each compound. This was done by checking them covered and is of a form that is easy to handle mathematiagainst a dead-weight gage tester at two bath temperatures cally. 100" C. apart. The true pressures a t all gage readings and temperatures were obtained from these calibrations. The volume of the vapor density bulb G and the connecting Apparatus parts which contained vapor when the isometrics were being measured-namely, the steel tee, valve E and its bellows, and the The apparatus used in the measurement of the isometrics upper half of the right-hand side of the U-leg D, was measured for each of the four compounds studied is shown in Figure 1: and found to be 4084 cc. a t 26" C. The volume of the bulb a t other temperatures was obtained from a measured temperature The vapor density bulb, G, was made of two hemispherical steel coefficient of expansion for the system. The change in volume of sections, about 1 j g inch (3.18 mm.) thick, which were copperthe system due to the expansion of the oil and mercury in U-leg welded together and then chromium-plated. I t was connected D was also corrected. The effect of pressure on the volume of the to the U-tube, D, and the external equipment through the steel sphere was calculated and found to be negligible over the range needle valves, E and F . Instead of the conventional packing, covered. these valves were made with a flexible steel bellows which was A check on leakage from the apparatus during each set of welded in place so that the valves were leakproof. The use of measurements was obtained by weighing the amount of material extension handles on valves E and F made it possible to operate introduced into and removed from the system. This is described them when they were in position in bath H . in the next section. U-tube D, through which pressure was transmitted from bulb G to gages A and B, w&s filled to a height of 4 inches (10.2 cm.) Procedure in each leg with mercury. The remainder of the leg connecting to the gages and the Bourdon tubes of the gages themselves were The following procedure was used in handling the comfilled before assembly with a medium-viscosity lubricating oil. pounds placed in the vapor density apparatus and in deterA valve, C, was placed in the line to the 0-100 pound gage, B , so mining their pressure-temperature relations at various denthat it could be isolated from the system when the pressure was beyond its range. sities: Bath H was equipped with the necessary heating coils, agitttor, The desired amount of material was transferred from one or and regulator to keep the temperature constant within 0.1 C. more of the sealed glass tubes or steel cylinders containing material of the highest degree of purity (3) to supply cylinder I This paper is the third in this series of artiolea (8, 3).
T
-
698
MAY, 1940
INDUSTRI-4L AND ENGINEERING CHEMISTRY
K . This container was weighed and connected to the system as shown in Figure 1. After valve E was closed and the vapor density apparatus was evacuated to a pressure of less than 0.1 mm., the maximum amount of material desired was introduced into the system. Valve F was then closed, and the greater portion of the vapor in the connecting lines was condensed in supply cylinder K by cooling it in a bath of solid carbon dioxide and acetone. The residual vapor was condensed in liquid air trap 0. The weight of material in the system was then determined from the change in weight of the supply cylinder and liquid air trap. E
TO
VACUUM PUMP
A TO MCLEOD
L
I
OF VAPORDENSITY APPARATUS FIGURE 1. DIAGRAM
The bath temperature was raised until it was about 5" C. above the saturation temperature a t the pressure indicated by gage A . Pressure readings were made a t constant temperature until three successive readings a t 5-minute intervals showed no change. The bath temperature was then raised the desired amount and another set of readings made. As a rule, four points were determined for each isometric, and a temperature range of 80" to 100" C. was covered. A barometer reading was obtained a t some time during the determination of each isometric. When each series of readings a t constant density had been completed, the desired amount of material (15 to 20 per cent of that originally present) was removed quantitatively from the apparatus and a new series of pressure-temperature relations determined. This was repeated a t from five to seven different densities for each compound. All pressure readings in the last two series of measurements were less than 100 pounds per square inch gage so that valve C was opened and gage B used. After the determination of the last isometric had been completed, the material remaining in the vapor density apparatus was removed quantitatively and weighed. The amount of material in the apparatus during each series of measurements was calculated from the weight of material initially introduced and the weight of the separate portions removed. The accuracy of these figures was checked by comparing the sum of the individual portions removed with the amount originally introduced. I n no case did the two vary more than 0.3 gram, and the average difference was less than 0.2 gram. This represented an error of 0.3 per cent in the isometric of lowest density and 0.06 per cent in the one of highest density. I n addition to giving an excellent means of checking the various vapor densities, these data also were evidence of the tightness of the system during each series of determinations. All temperatures were measured with mercury thermometers having an accuracy of 0.1 O C. over their entire ranges as
69%
TABLEI. EQUATION-OF-STbTE CONSTANTS OF CHClFs, CHCI,F, CClsF, AND CCl2F-CClF3 Compound CHClFe CHClzF CClaF CClzF-CClFz
Constants ----
Mol. Wt.
BO
a
BO
86.46 102.92 137.37 187.37
12.69 20.54 32.95 37.50
-0,299 -0.179 f0.194 -0,062
0.185 0.286 0.572 0.534
k
b -0.917 -0.497 10.287 -0.223
0.991C,
. .. ... ...
determined by comparison with a platinum resistance thermometer which had been calibrated by the Sational Bureau of Standards. 811 pressure readings were estimated to the nearest tenth of the smallest scale division, which was 1 pound in the case of the 0-100 pound gage and 2 pounds in the case of the 0-300 pound gage. All pressures were converted t o , absolute units with the aid of a standard mercury barometer.
Results With the apparatus and procedure described, between five. and seven isometrics were determined for each of the four compounds under investigation. These isometrics covered the pressure range of 3.5 t o 21 atmospheres and a temperature. range of 40" to 100" C. above the corresponding saturation temperature for each isometric. Data thus obtained were used to calculate for each compound the constants of a Beattie-. Bridgeman type of equation of state of the form:
where p = pressure, atm. abs. T = temperature, K. = ' C. V = liters per gram mole R = 0.08206
+ 273.10
TABLE11. VAPORDENSITYOF CHCIFi p
= (0.013796 T
+
-
+ 0.08132 T D
-
3.794)Da (0 015044 T 12.69)D2 D = moles per liter, mol. weight = 86.46
Vapor Density Moles/Ziter
Deviation from Calcd
c.
Calcd. p Aim.
Obsvd. p Atm.
0.9192
51.7 65.1 78.8
18.22 19.53 20.88
18.20 19.55 21.00,
+O. 1
0.8404
48.4 65.1 78.4 93.3
16.88 18.35 19.54 21.01
-0.1 -0.1 i-0. 1
0.7064
41.1 74.6 107.7 136.9
16.89 18.36 19.53 21.02 14.27 10.60 18.92 20.95
14,28, 18.95 20.93.
108.3 139.9
11.40 13.26 l5,29 16.92
11.35 13.29 15.2Y 16.88
+O. 1 +0.5, t0.2 -0. I -0.4 f0.2 0.0. -0 2
32.0 68.7 105. 9 138 2
8.79 10.13 11 49 12 67
8.80. 10.17 11.48 12.66
0 5533
0.4071
t O
33.6
as.+
16.68
0 . 2733
32.0 56.7 76.2 98.0
6.184 6.768 7.229 7.744
6.163. 6.155 7.218 7.748
0.1916
4.484 5.146 5.681 6.191
4.476 5.150 5.673 6.184
0.08490 0.06139 0.04647 0.04207 0.04198 0.03130 0.03057
33.5 74.3 107.3 138.7 26.5 131.0 131.0 25.1 26.1 131.0 130.8
2.010 1.993 1.513 1.006 1.007 1.022 0.998
2.007 1.991 1.513 1.004
0.02231 0.02071 0.02009 0.01196 0.01196 0.01085
24.7 131.0 130.8 24.7 131.0 130.7
0,5362 0.6777 0.6572 0.2885 0.3921 0 3457
1.00s
1.02,o 0.996 0.5359. 0.6764 0.6578 0.2889 0.3922. 0.3451
% -0.1
+0.6
0 . (I
+o.
1
+0.4 -0.1
-0.1
-0.3. -0.2 -0.2 +o. 1 -0.2
+o. 1: -0.1 -0.1
-0.1 -0.1 0.0 -0.2 +O. 1 -0.2 -0.2 -0.1 -0.2 fO. 1 +O. 1 0.0
-0.2
INDUSTRIAL AND ENGINEERING CHEMISTRY
700
TABLEV. VAPORDENSITYOF CCl2F-CClFz
TABLE 111. VAPORDENSITY OF CHClzF = (0.011666 T
p
- 3.677)D + (0.02347 T - 20.54)02 + 0.08206 T D .Mol. weight = 102.92
Vapor Density Mole~/liter 0.8551 0.6950
0.5521
0.3929
0.2335
0.1430
0.06654 0.05674 0.04345 0.04314 0.04240 0.04203 0.02926 0.01996 0.01560 0.01079
t
c.
127.2 133.8 119.1 137.7 158.3 173.2 107.4 125.6 150.4 172.3 93.5 115.7 135.5 155.1 70.5 91.4 115.0 155.2 53.0 70.7 109.9 155.5 23.4 23.1 23.4 23.0 25.6 25.7 23.0 25.6 23.0 25.5
p = (0 009772
Vapor Density Moles/liter
% $0.1 4-0.3 +o. 1
4-0.4 1 0.0
+o. 1
4-0.4 +0.2 +o. 1 0.0 1
+0.2 -0.2 0.0 -0.2 +0.3 0.0 -0.6 -0.1 0.0 +o. 1 -1.0 -1.0 -1.1 -0.8 -0.9 -1.0 -0.5 -0.6 -0.2 -0.3
-
TABLE IV. VAPORDENSITYOF CClsF
(6.392
- 0.013471 T)D* + (0.04694 T - 32.95)D'
Vapor Denaity Molce/liter 0.7946 0.6480
0.5400
0.4461 0.4069
0.2236
0.1355
0.09653 0.07570 0.07468 0.07066 0.06697 0.04199 0.03975 0.03777
Mol. weight
1
c.
147.9 155.6 164.1 138.2 155.6 171.6 190.5 203.5 129.6 154.8 183.6 203.6 123.3 157.0 115.6 136.8 158.8 183.6 88.4 123.6 159.0 178.2 67.6 104.0 140.5 178.2 60 46.3 45.0 45.0 60.1 29.9 44.8 60.0
-
137.37
Obsvd. p Atm. 19.51 20.25 21.03 16.33 17.59 18.74 19.96 20.86 13.84 15.29 16.88 17.97 11.71 13.24 10.65 11.47 12.38 13.32 5.830 6.558 7.286 7.680 3.483 3.939 4.354 4.803 2.49 1.879 1.847 1.758 1.764 1.013 1.013 1.013
Calcd. p Atm. 19.49 20.16 20.91 16.37 17.58 18.69 19.99 20.89 13.90 15.31 16.92 18.04 11.75 13.26 10.62 11.48 12.36 13.36 5.851 6.574 7.301 7.696 3.481 3.916 4.352 4.803 2.479 1.876 1.850 1.755 1.754 1.011 1.009 1.008
A = Ao (1 B = Bo (1
-
Deviation from Calcd.
181.6 194.3
19.69 20.95
0.6987
176.1 187.8 201.6 214.7
17.65 18.69 19.82 20.90
17.63 18.69 19.81 20.90
-0.1 0.0 -0.1 0.0
0.5801
167.4 183.6 200.2 214.6
15.21 16.25 17.32 18.24
15.22 16.26 17.33 18.24
+O.l
0.4025
150.3 170.7 193.2 214.2
11.02 11.85 12.77 13.63
11.05 11.88 12.78 13.63
4-0.3 +0.3
138.0 163.2 191.8 214.2
8.79 9.57 10.45 11.14
8.78 9.57 10.46 11.14
0.2158
a
Calcd. p Atm.
0.8031
0.3176
_ _ ~ p
- 2.329)Da + (0.04382 T - 3 7 . 5 6 ) D + 0.08206 TD Obsvd. p Atm. 19.76 20.97
+o.
+o.
T
.Mol. weight = 187.37
Deviation from Calcd.
Obsvd. P Atm. 20.59 21.25 17.21 18.61 20.05 21.12 13.84 14.88 16.20 17.38 10.01 10.84 11.57 12.25 5.91 6.33 6.84 7.65 3.544 3.776 4.259 4.823 1.543 1.322 1,021 1.015 1.006 0.997 0.6961 0.4807 0.3750 0.2621
Calcd. p Atm. 20.56 21.19 17.20 18.54 20.03 21.11 13.83 14.82 16.17 17.36 10.01 10.83 11.55 12.27 5.91 6.34 6.82 7.65 3.564 3.781 4.261 4.819 1.559 1.335 1.032 1.023 1,015 1.007 0.6993 0.4838 0.3757 0.2628
VOL. 32, NO. 3
1
c.
% +0.4 +o. 1
+o. 1 +o. 1 0.0
+o.
1 0.0
-0.1 0.0
+o.
1 0.0
118.0 146.0 178.2 204.0
5.990 6.545 7.185 7.697
5.946 6.537 7.197 7.707
+o. +o.
0.1523
104.2 134.9 170.1 204.0
4.233 4,648 5.125 5.585
4.231 4.667 5.143 5.612
0.0 4-0.4 +0.4 +0.5
0.06864 0,02805 0.02802 0.01518 0.01516 0.01515 0.01421
85.69 42.20 86.20 21.23 62.69 87.18 25.3
1.916 0.7071 0.8090 0.3610 0.4125 0.4429 0,3430
1.9070 0.7030a 0.80726 0.3596a 0.4120' 0.4429a 0.3439
-0.5 -0.6 -0.2 -0.4 -0.1 0.0 +0.3
-0.7 -0.1 2
1
Riedel (6).
f 0.08206 TD Deviation from Calcd.
%
+o.
1
4-0.4 +0.6
-0.2 1 +0.3 -0.2 -0.1 -0.4 -0.1 -0.2 -0.4 -0.3 -0.2 +0.3 -0.1 +0.2 -0.3 -0.4 -0.2 -0.2 -0.2
+o.
+o.
1 +0.6 0.0 0.0
+0.4 f0.2 -0.2 f0.2 +0.6
+0.2 +0.4
4-0.5
$)
9)
The values of the constants Ao,a, Bo, and b are recorded in Table I. The method used in their calculation was similar
to that of Buffington and Gilkey (4). In the case of CHClF2, it was found necessary to use an additional constant, k , as a multiplier of R in order to bring the data calculated a t low pressures into agreement with the observed values. This corrected for the deviation of the CHCIFz vapor from the ideal gas law a t low pressures. The value of constant k is given in Table I. By substituting in Equation 1 the respective values of A and B as given in Equations 2 and 3 and simplifying, the following expanded form of the equation of state is obtained:
The equations obtained for each compound by the substitution of its constants in Equation 4 are shown in Tables I1 to V. The pressures calculated from these equations a t various densities and temperatures and the corresponding observed pressures are also given. The excellence of the agreement between the calculated and observed pressures is shown by the fact that the average difference for all four compounds is less than 0.3 per cent. The vapor density measurements made on CHCIFz at low pressures (0.3 to 2 atmospheres) showed that it had an apparent molecular weight of 87.25 instead of the theoretical value of 86.46. This indicated the presence of an impurity in the CHC1F2. Further purification by fractionation at pressures of 1 and 0.2 atmosphere was performed, but the various fractions had the same apparent molecular weight. Removal of impurities by partial hydrolysis of the CHCIFz with a 20 per cent aqueous solution of sodium hydroxide was also tried with similar results. A chemical analysis for chlorine and fluorine was attempted but the results were not of sufficient accuracy to be conclusive. Consequently, the use of k was resorted t o
1vLAl-, 1940
INDUSTRIAL AND ENGINEERING CHEMISTRY
701.
measurement of the pressure, temperature, and density of SATURATED VAPOR DENSITY OF FLUOROCHLOROthe vapor sample. The data obtained, together with the corHYDROCARBONS responding pressures as calculated from the equations of Compound Temp. Satd. Yapor Density state, are shown in Tables I1 t o V. c. Gram/cc. A few saturated vapor density measurements were made a t CHClzF 132.2 0.105 high pressures and densities by determining the dew points 159 0.196 167 0.299 of samples contained in sealed glass tubes. Weighed quanti136.2 0.08'3 CClsF ties of material were sealed in clean glass tubes of known vol0.193 173.1 0.200 176.0 ume, and the temperature a t which the liquid was completely 0.241 182.4 vaporized was determined with an estimated accuracy of 0.159 180.1 CCIzF-CCIF2 * 0.3" C. Measurements were made on CHCl,F, CC13F, and 0.244 198.2 0.292 204.4 CClZF-CClF2 a t densities between 0.1 and 0.3 gram per cc. The results are given in Table VI. The only published data on the P-V-T relations of any of these compounds are those of Riedel (6) on CC12F-CCIFt. A in correlating the equation of state with the experimental comparison of representative values from his data and values data. At present no explanation has been found for the calculated from our equation of state is given in Table V. anomalous molecular weight of CHClF2. Literature Cited Other Vapor Density Measurements (1) Beattie, J. A,, and Bridgeman, 0. C.. J . Am. Chem. SOC. SO, 3133-8 (1928). A number of additional vapor density measurements were (2) Benning, A. F., and McHarness, R. C.. IND. Eso. CHEM.,31, made on all of the compounds by the Dumas method. They 912-16 (1939). were carried out a t pressures ranging from 0.25 to 2.5 atmos(3) Ibid., 32, 497 (1940). pheres and a t temperatures between 20' and 130" C., in a (4) Buffington, R. M., and Gilkey, W. K., Ibid., 23, 254-6 (1931)'. (5) Riedel, L.,2. ges. K b l t e - I d . , 45, 221-5 (1938). calibrated glass container of approximately 525 cc. capacity. The usual precautions were taken to ensure the accurate CONTRIBUTION 4 from Kinetic Chemicals, Ino.
TABLEVI.
THE ALCHEMIST By HARRYCIMINO
T h r o u g h the courtesy of Mr. Walter Yust, cditorof the Encyclopedia Britannica, we are enabled to reproduce a very recent pen-and-ink drawing which the latter used last year in an information circular. The original of this, No. 113 in the Berolzheimer series of Alchemical and Historical Reproductions, is 6 by 8 inches. The artist, Harry Cimino of Falls Villagc. Connecticut, has with a minimum of apparatus, nicely shown the alchemist ac his studies, while at the same timc avoiding the usual clutter present in most alchemical paintings.
D. D. BBROLZHEIMER 50 East 41% Street
New York, N. Y.
A list of the first % rc roductions a pcarcd in our January. 1939, issue, page 124. T h e fist of rcpmfuctionr 97 to 108 ipppeirr i n January, 1940, page 134. An additional reproduction rppcars each month.
