Phase Equilibria in Hydrocarbon

The consistency of the results was tested by crom plotting values from the smooth curves with respect to composition. The isobaric-isothermal curves o...
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688

INDUSTRIAL A N D E N G I N E E R I N G C H E M I S T R Y

i t breaks. There is thus an optimum amount of hardening for permitting the maximum effective stretch to be applied. This was shown by an experiment in which the maximum degree of stretch that could be applied to the fibers was determined a t 5minute intervals aFter immersion in a quinone solution under various conditions. The maximum extension of about 300% was attained in 30 to 45 minutes at 2 2 O , 15 to 35 minutes a t 35O, and 10 minutes at 50" C. in 1% quinone, but it was attained in less than 5 minutes a t 50" in 2% quinone. Stretch should be applied under any of these combinations of temperature and time to be of most benefit. If the fiber is to be stretched not more than 100~o, however, there is considerable latitude in the time a t which stretch may be applied. The reaction of quinone with casein appears to be irreversible in neutral solutions. Casein fiber hardened with quinone is superior to formaldehyde-hardened fiber with respect to brittleness and resistance to water. Quinone hardening was most effective near the isoelectric point of casein. Although the nature of the reactions is still unknown, quinone has been found to react with proteins and many amino compounds ( I , 2); most of these reactions proceed readily in aqueous solution a t room temperature. It has been found (4, 6) that deaminized collagen (hide powder) fixes about 60% of the amount of quinone fixed by untreated collagen in 24 hours. It is thus probable that the e-anino groups of

Vol. 37, No. 7

lysine are available in proteins for reactions of this type, but that they account for only part of the reaction. The modification of casein by acetylation, deamination, or esterification, as well ss the addition of small quantities of quinone or formaldehyde, markedly decreases the ability of cssein to form fibers in the presence of water. ACKNOWLEDGMENT

The authors are greatly indebted to R. Hellbach and N. J. Hipp of this laboratory for designing and constructing the equipment used in this development. Also they wish to record their gratitude to Alice Wolferd, Helen Dearden, and Edith Polis for valuable aid. LITERATURE CITED

H.,Ber., 43,525 (1910). (2) Meunier, L.,and Seyewetz, A., C m p t . rend., 146, 987 (1908). (3) Millar, A.,J. SOC.Chem. I n d . , 18, 16 (1899). (4) Thomas, A. W., and Foster, S. B., J. Am. Chem. Sac., 48, 489 (1926). (5) Thomas, A. W., and Kelly, M. W., IND.ENQ.CHEM.,16, 925 (1924). (6) Todtenhaupt, F.,German P a t e n t 170,051(1904). (1) Fischer, E., and Schrrtder,

PBESENTED at a meeting eponaored by the American Society for Teating Materials, Philadelphia Distriot Committee, September, 1943.

Phase Equilibria in Hydrocarbon J

Systems J

VOLUMETRIC BEHAVIOR OF ETHANE-CARBON DIOXIDE SYSTEM

T

HE widespread occurrence of carbon dioxide in natural gas mixtures from petroleum reservoirs makes desirable a more complete knowledge of carbon dioxide-hydrocarbon systems. Data from the published literature are sparse. Sander (9) and Wan and Dodge (11) investigated the solubility of carbon dioxide in benzene. The volumetric behavior of the methanecarbon dioxide system was recently studied ( 6 ) . The work reported here represents the second of a proposed series of investigations undertaken by the authors' laboratory for the purpose of establishing the general behavior of carbon dioxide in hydrocarbon systems. Ethane, obtained from the Carbide and Carbon Chemicals Corporation, w m subjected to triple fractionation at atmospheric pressure with a reflux ratio of approximately 50 to 1 in a Pfoot, vacuum-jacketed column packed with glass rings. Initial. and final cuts amounting to 10% of the charge in the kettle were discarded in each fractionation. The overhead was condensed in vacuo at liquid air temperatures with continuous removal of any condensable gases which might have accumulated during the condensation process. The purity of the material so obtained was verified by the constancy of its vapor pressure. AB 80' F. the observed bubble-point and dew-point pressures differed by less than 0.3 pound per square inch. Carbon dioxide was prepared by the thermal decomposition of

reagent-grade sodium bicarbonate. The gas was dried a t atmospheric pressure by passage in succession through a water trap a t 32' F., a tube packed to a depth of 12 inches with calcium chloride, and a similar tube packed with barium perchlorate. The dried gas WM then condensed in vacuo a t liquid air temperatures with continuous evacuation of noncondensable gases. The resulting material had a vapor pressure at 32' F. which differed from that of pure carbon dioxide by less than 0.1 pound per square inch. EQUIPMENT AND PROCEDURE

A detailed descript,ion of the apparatus has been published (8). No changes in the equipment were necessary for the present work. The components of the mixtures were introduced gravimetrically into the volumetric apparatus from small steel sample bombs which could be weighed directly upon an analytical balance. Great care was excrcised in preparing the mixtures. The equilibrium cell and connecting lines to the sample bombs were evacuated to an absolute pressure of 10-4 mm. of mercury before admitting the sample. Residual gas left in the connecting lines was condensed back into the sample bomb by means of liquid air. The change in the weight of the sample bomb was determined upon an analytical balance using the method of tares and

H. H. REAMER, R. H. OLDS, B. H. SAGE, AND W. N. LACEY California Institute of Technology, Pasadena, Calv.

INDUSTRIAL AND ENGINEERING CHEMISTRY

July, 1945

689

TABLEI. COMPRESSIBILITY FACTORS FOR MIXTURES OB ETHANE AND CARBON DIOXIDE Compressibility Faotor a t 100' F. with Mole Fraotion Ethane an Follows: 0.1777 0.8313 0,6132 0.6763 0.8280 1.0000 1.0000 1.0000 1.0000 1.0000 0.9268 0.9181 0.9380 0.9336 0.9398 0.8206 0,8667 0.8404 0.8678 0.8726 0.6994 0.7666 0.7371 0.7961 0.7863 0.6347 0.6649 0.6086 0.7030 0.6894 0.4387 0.3167 0.6718 0.6207 0.6896 0.3006 0.4460 0.3602 0.6190 0.6020 0.3331 0.3046 0.4246 0.3799 0,4360 0.3307 0.3100 0.3934 0.3623 0.3929 0.3164 0.3617 0.3311 0.3682 0.3687 0.3364 0.3279 0.3464 0.3459 0.3226 0.3420 0.3466 0.3395 0.3488 0.3162 0.3668 0.3428 0.3668 0.3668 0.3161 0.3694 0.3721 0.3494 0.3669 0.3220 0.3761 0.3800 0,3639 0.3717 0.3261

Preasure,

In. Lb''*Abs. q*

.

0 200 400 600 800 1,000 1,100 1 2oe 1'260 1:300 1,400 1,600 1600 1:700 1,760 Prwure, Lb./Sq. In. Abs. 0 200 400 600 800 1,000 1,260 1,600 1760 2:ooo 2 260 2:aoo 2,760 3,000 3,600 4,000 4,600

6,000

6,000 7,000 8,000 9,000 10,000

0 200 400 600 800 1,000 1,250 1 600 1:760 2,000 2,260 2,500 2,760 3,000 3,600 4,000 4,600 5,000 6,000 7,000 8,000 9,000 10,000

. 0 . 1 7 7 7 . 8 2 8 8 160'-.F 1.0000 1* 0000 1.0000 1.0000 0.9666 0.9651 0.9623 0.9479 0.9111 0.9078 0.9016 0.8921 0.8632 0.8682 0.8464 0.8316 0.8127 0.8063 0.7868 0.7664 0.7686 0.7496 0.7246 0.6963 0.6893 0.6779 0.6499 0.6110 0.6204 0.6109 0.6828 0.6449 0.6697 0.6684 0.6403 0.6123 0.6207 0.5286 0.6234 0.6097 0.6039 0.6202 0.6262 0,6232 0. 6040 0.6269 0.6410 0 . 6449 0.6162 0. 6424 0.6616 0.6710 0.6317 0.6621 0.6862 0. 6990 0.6727 0.6086 0.6393 0.6681 0.6193 0.6691 0.6961 0.7190 0.6676 0.7119 0.7631 0.7813 0.7176 0.7666 0.8113 0,8439 0.8187 0.8732 0.9297 0.9697 0.9180 0.9793 1.0439 1.0920 1.0177 1.0881 1.1880 1.2122 1.1129 1.1893 1.2714 1.3310 1 ,2069 1.2948 1.3838 1.4466

-

1.0000 0.9683 0.9368 0,9030 0.8697 0.8370 0.7965 0 * 7679 0.7222 0.6914 0.6676 0.6604 0,6420 0.6412 0.6668 0.6837 0.7186 0.7673 0.8418 0.9303 1.0199 1.1060 1.1906

0.9608 0.9202 0.8783 0:8362 0.7962 0.7468 0.7047 0.6719 0.6503 0.6412 0.6438 0.6633 0.6679 0.7096 0.7674 0.8094 0.8621 0.9697 1.0799 1,1890 1.2976 1.4067

0.1777 0.3600 0.3779 0.4069 0.4360 0.4651 0.6236 0.6819 0.6401 0.6973 0.8107 0.9221 1.0306 1.1376 1.2412

6,000

6.000 7,000 8,000 9,000 10.000

3

#

I

0 . 9666

0.9113 0.8649 0.8184 0.7721 0.7186 0.6729 0.6400 0.6231 0.6213 0.6290 0.6447 0.6642 0.7140 0,7697 0,8272 0.8866 1.0031 1.1204 1.2367 1.3616 1.4663

1.0000 0.9836 0.9673 0.9612 0.9354 0.9197 0.9008 0.8836 0.8679 0.8647 0.8430 0.8336 0.8271 0.8229 0.8212 0.8291 0.8430 0.8634 0.9170 0.9790 1.0466 1.1169 1.1862

1.0000 0.9822 0.9648 0.9477 0.9310 0.9161 0.8967 0.8796 0.8660 0.8623 0.8420 0.8346 0.8296 0.8278 0.8314 0.8466 0.86110 0.8879 0.9479 1.0176 1.O90b 1.1662 1.2420

-340' F.1.0000 0.9803 0.9608 0.9418 0.9234 0.9064 0.8862 0.8683 0.8534 0.8411 0.8319 0.8260 0.8230 0.8241 0.8342 0.8624 0.8787 0.9094 0.9791 1.0667 1.1403 1.2226 1.3038

0.3313

-

I

1.oooo 1.0000 1.0000

0.9642 0.9277 0.8903 0.8629 0.8166 0.7701 0.7316 0.6986 0,6742 0.6689 0.6638 0.6676 0.6676 0.6971 0.7406 0.7886 0.8376 0.9368 1.0391 1.1419 1.2437 1.3440

Compressibilit Faotor with Mole Fraction E t t a n e aa Follows: 0.3313 0.6132 0.6763 0.3797 0.4026 0.4114 0.4087 0.4346 0.4478 0.4394 0.4677 0.4842 0.4707 0.6017 0.6209 0.5017 0.6360 0.5674 0.6644 0.6041 0.6307 0.6270 0.6726 0.7031 0.6891 0.7400 0.7741 0.7509 0.8066 0.8440 0.9362 0.8732 0.9810 1.0630 0.9911 1.1159 1.1070 1.1884 1.2473 1.2212 1.3132 1.3762 1.3333 1.4383 1.5038

Corn ressibility Faotor with Mole Fraotion Ethane as Follows: 0.1777 0.3313 0.5132 0.6763 0.8280 0.1777 I 280' $. 1.0000 1.0000 1.0000 1.0000 1,ooo'o 1,0000 1.0000 0,9883 0.9420 0.9776 0.9767 0.9734 0.9706 0.9676 0.9646 0.9612 0.9466 0.9409 0 * 9349 0.9768 0.8797 0.9316 0.9271 0.9201 0.9117 0.9026 0.9654 0.8117 0,9639 0.7368 0.9088 0.9031 0.8938 0.8829 0.8711 0.9433 0.8866 0.8804 0.8691 0.8554 0.8409 0.6663 0.8694 0.8636 0.8401 0.8236 0.8062 0.9308 0 . 6607 0,4996 0.8342 0.8288 0.8148 0.7961 0.7757 0.9196 0.8114 0.8062 0.7931 0.7732 0.7618 0.9087 0.4834 0.7916 0.7876 0.7763 0.7661 0.7349 0.8996 0.4941 0.6166 0 * 7746 0.7728 0 7620 0.7462 0.7268 0.8917 0.8862 0.6463 0.7616 0.7622 0.7640 0.7398 0.7240 0.7624 0.7664 0.7610 0.7400 0.7288 0.8809 0.6766 0 7473 0.7666 0.7636 0.7463 0.7390 0.6090 0.8781 0 * 7479 0.7633 0.7703 0.7692 0.7714 0.6748 0.8771 0.7601 0.7826 0.7980 0 8038 0.8113 0.8831 0.7416 0.7838 0.8088 0.8326 0.8447 0.8673 0.8086 0.8944 0.9100 0.8123 0.8411 0.8705 0.8893 0.9067 0,8763 0.8784 0.9161 0.9666 0.9838 1.0096 0.9627 1.0073 1.0040 0.9626 0.9969 1.0462 1.0807 1,1161 1.1370 1.0306 1.0802 1.1377 1.1790 1.2204 1.0620 1.2660 1.1089 1.1666 1.2293 1.2766 1.3262 1.1230 1.3911 1.1861 1.2600 1.3186 1.3748 1.4278 1.1848 1.6144

220' F. 1.0000 0.9670 0.9330 0.8986 0.8639 0.8299 0.7890 0.7606 0.7166 0.6886 0.6696 0.6684 0.6666 0.6687 0.6810 0.7137 0.7633 0.7974 0.8885 0.9826 1.0779 1.1723 1.2653

Preseure, Lb./Sp. In. Abs. 2,000 2 260 2:500 2,760 3,000 3 600 4:OOO 4,500

1.0000 0.9871 0.9746 0.9623 0.9508 0.9394 0,9269 0,9155 0.9060 0.8976 0.8912 0.8863 0.8836 0.8825 0 8854 0.8949 0.9113 0.9318 0.9809 1.0386 1.1029 1.1706 1.2396 I

0.8280 0.4192 0.4590 0.4985 0.5380 0.5773 0.6546 0.7310 0.8061 0.8803 1.0265 1.1711 1.3124 1.4497 1.5821

-

0 6763 0 828;

0.5132 400' F. 1.0000 0.9865 0.9714 0.9578 0.9447 0.9329 0.9191 0,9071 0.8965 0,8880 0,8818 0.8782 0,8770 0.8778 0.8861 0,9009 0.9213 0,9466 1.0062 1.0744 1.1467 1.2206 1.2947

1IO000 0.9838 0,9679 0,9530 0.9385 0.9250 0.9100 0,8966 0.8855 0.8771 0.8717 0.8688 0,8686 0.8701 0,8819 0 , '3003 0.9240 0.9530 1,0224 1.0978 1.1772 1.2679 1.3400

1~0000 0.9820 0,9644 0,9476 0.9316 0.9170 0.9006 0.8865 0.8757 0.8671 0.8616 0,8600 0,8608 0,8646 0,8794 0 . 90.30 0.9325 0.9660 1.0416 1.1258 1.2106 1.2966 1.3844

1.0000 0.9897 0.9797 0.9702 0.9612 0.9526 0.9431 0.9350 0.9281 0.9223 0.9184 0.9160 0.9156 0.9168 0.9241 0.9374 0.9565 0.9795 1.0324 1.09l6 1.1558 1.2233 1.2928

1,0000 0.9884 0.9772 0.9664 0.9563 0.9471 0.9367 0.9277 0.9206 0.9149 0.9113 0,9098 0.9095 0.9118 0.9216 0.9379 0.9590 0.9842 1.0433 1.1105 1.1814 1,2557 1.3307

1.0000 0.9869 0.9743 0.9623 0.9511 0.9408 0.9293 0.9191 0.9116 0.9059 0.9031 0.9025 0,9037 0.9079 0.9211 0.9421 0.9681 0.9967 1.0622 1,1345 1.2124 1.2929 1,3757

1

1.0000 0.9782 0.9666 0.9366 0.9162 0.8960 0.8741 0.8560 0.8393 0.8273 0.8187 0.8138 0.8136 0.8163 0.8308 0.8539 0.8847 0.9211 1.0016 1.0865 1.1763 1..2646 1.3647

1.0000 0.9768 0.9619 0.9286 0.9062 0.8858 0.8619 0.8422 0.8269 0.8144 0.8057 0.8020 0.8016 0.8064 0.8276 0.8696 0.8950 0.9360 1.0246 1.1167 1.2106 1.3064 1.4024

1.0000 0.9918 0.9838 0.9760 0.9684 0.9613 0.9527 0.9461 0.9382 0.9318 0.9266 0.9223 0.9192 0.9179 0.9190 0.9261 0.9347 0.9481 0.9822 1.0277 1.0780 1.1305 1.1837

1.0000 0.9910 0.9823 0.9739 0.9658 0.9685 0.9501 0.9426 0.9358 0.9308 0.9264 0.9231 0.9216

80.9340 :X

0.9479 0.9644 1.0103 1.0616 1.1176 1.1786 1.2412

immersed in a rapid-circulation oil bath whose temperature substitution weighing. Air buoyancy corrections were applied to the stainless steel weights, which had been calibrated against was maintained with a maximum fluctuation of 0.05' F. by a 100-gram weight certified by the National Bureau of Standelectronically controlled thermostats. The temperature was ards. Comparison of the sample weight measured by addition measured by a platinum resistance thermometer calibrated at the start of a test and by withdrawal at the end of a test against a similar instrument certified by the National Bureau indicated that this quantity was known with an uncertainty of of Standards. The resistance of the thermometer was meas0.01 gram in a total sample weight of 100 grams. ured with a Mueller bridge, and the corresponding temThe volume of the sample was determined by the volume of perature waa computed from interpolations between calibration mercury displaced from the equilibrium cell. The specific points on the basis of the Callendar equation ( 8 ) . It is believed volume of mercury at the pressures and temperatures involved that the absolute temperature in terms of the international temin the experimental observations was computed from the values perature scale was known with an uncertainty less than 0.loF. given in the Smithsonian Tables for mercury at atmospheric Pressure waa determined with a rotating cylinder and piston pressure with corrections for the compressibility of mercury in hydraulic balance. The balance was calibrated against a meraccordance with the data of cury manometer at presSmith and Keyes (f0). It sure8 up to 50 pounds per is estimated that the volume Five mixtures of ethane and carbon dioxide were studied square inch absolute and occupied by the sample was with regard to their volumetric properties in the temperaagainst the vapor pressure of measured with an uncerture interval from 100' to %OD F. at pressures up to 10,000 pure carbon dioxide at 32' F. tainty not exceeding 0.2%. pounds per square inch. The results are tabulated in using Bridgemans value of The equilibrium cell was terms of compressibility factors and molal volumes. 505.56 pounds per square inch

690

INDUSTRIAL AND ENGINEERING CHEMISTRY

Prensure, Lb./Bq. In. Abs. 14.696 200 400 600 800 1,000 1,250 1500 1:750 2,000 2,250 2,500 2,750 3,000 3,500 4,000 4,500 5,000 6,000 7,000 8.000 9,000 10.000 14.698 200 400 000 800 1,000 1,250 1,500 1,750 2,000 2,250 2,500 2,750 3,000 3,500 4,000 4,500 5,000 6,000 7,000 8,000 9,000 10,000

Pressure Lb./Sq. In. Abs. 14.696 200 400 600 800 1,000 1,250 1,500 1,750 2,000 2,250 2,500

TABLE 11. MOLALVOLUMES

-

0.1777 0.3313 0.5132 100' F. 406,99 406,95 406.85 28.23 28.17 28.04 13.102 13.031 12.866 7.960 7.872 7.663 5.278 5.176 4.917 3,541 3.435 3.128 1.8880 1.8904 1.7410 1.2622 1,3595 1.3907 1.1193 1.2147 1.2758 1.0512 1.1404 1.2091 1,0088 1.0911 1,1599 0.9776 1.0557 1.1237 0.9523 1.0281 1.0958 0.9312 1.0045 1.0732 0.8984 0.9080 1.0307 0,8738 0.9415 1,0099 0.8544 0.9198 0.9878 0.8377 0.9021 0.9690 0.8116 0.8742 0.9372 0.7912 0.8504 0.9121 0.7738 0.8312 0.8923 0.7592 0.8150 0.8764 0.7455 0,8009 0.8639

-

451.12 31.81 15.148 9.568 6.756 5.045 3.667 2.751 2.1270 1.7315 1.4894 1.3407 1.2459 1.1787 1.0882 1.0297 0.9865 0.9545 0.9075 0.8722 0.8460 0.8224 0.8020

451.08 31.76 15.093 9.512 6.695 4.985 3.607 2.709 2.1221 1.7574 1.5376 1.4017 1.3117 1.2461 1,1562 1.0958 1.0521 1,0195 0.9679 0.9304 0.9021 0.8788 0.8611

0.1777 671.21 48.95 24.276 16.055 11.948 9.488 7.523 6.219 5.292 4.598 4.064 3.641

160' F. 450.99 31.67 14.990 9.382 6.541 4.819 3.458 2,584 2.0533 1.7404 1.5553 1.4392 1.3582 1.2973 1.2148 1.1573 1.1130 1.0791 1.0305 0.9918 0.9627 0.9395 0.9203

FOR

ETHANE-CARBON DIOXIDE

406.67 27,83 12.620 7.379 4.569 2,635 1.5891 1.3835 1.2909 1.2356 1.1954 1.1034 1.1378 1.1160 1.0824 1.0558 1.0333 1.0139 0.9821 0.9575 0.9365 0.9185 0.9033

Molal Volume with Mole Fraction Ethane a8 Follows: 0.8280 0.1777 0.3313 0.5132 0.6763 0.8280 0.1777 r 220° F. - . c 406.44 495.22 495.16 495.07 494.96 494.81 583.29 27.67 35.32 35 27 35.17 35.04 34.89 42.21 12.321 17.065 17.014 16.918 16.781 16.618 20.754 7.002 10.978 10.925 10.824 10.678 10.815 13.606 4,015 7.930 7.877 7 777 7.624 7.462 10.035 1,8903 6.106 6.064 5.949 5.801 5.632 7.893 1.4896 4.648 4.604 4.494 4.358 4.193 6.185 1.3695 3,680 3.650 a. 557 3.427 3.272 5.056 1.3043 3.010 2.987 2.912 2.801 2.668 4.256 1.2590 2.522 2.511 2.4589 2.3718 2.2726 3.668 1,2253 2.1640 2.1705 2.1361 2.0787 2.0142 3.216 1.1977 1.8977 1.9211 1.9076 1.8785 1.8353 2.862 1.1751 1.7029 1.7387 1.7440 1.7329 1.7101 2.581 1.1559 1.5591 1.6016 1.6232 1 ,6240 1.6150 2.3541 1.1234 1.3688 1.4193 1.4528 1.4787 1.4881 2.0137 1.0977 1.2468 1.3015 1,3504 1.3812 1.4036 1.7789 1.0760 1.1647 1.2211 1,2781 1.3120 1.3409 1.6078 1.0575 1.1048 1.1633 1.2218 1.2577 1.2918 1.4820 1.0276 1.0234 1.0802 1.1389 1.1789 1.2195 1.3117 1.0049 0.969l 1.0238 1.0828 1.1253 1.1675 1.2003 0.9854 0.9299 0.9828 1.0412 1.0841 1.1276 1.1227 0.9675 0.8964 0.9501 1.0080 1.0516 1.0955 1 0641 0.9503 0.8685 0.9230 0.9804 1.0254 1,0688 1.0172

450.86 31.52 14.832 9.216 6.363 4.624 3.251 2.4159 1.9469 1.6949 1.5465 1.4495 1.3809 1.3279 1.2505 1.1954 1.1547 1.1225 1.0748 1.0375 1.0077 0.9835 0.9614

480.67 31.32 14 626 8.997 6.125 4.368 2.983 2.2151 1.8371 1 .ti430 1.5267 1,4506 1.3944 1.3500 1.2822 1.2328 1.1949 1.1642 1.1168 1.0802 1.0516 1.0279 1.0072

0.6763

I

I

-

I

280' F. 539.28 38.80 18.945 12.326 9.018 7.037 5.458 4.415 3.681 3.142 2.733 2.4183 2.1719 1.9774 1.6963 1.1085 1.3827 1.2897 1.1022 1.0803 1.0226 0.9781 0.9416

Molal Volume a t 460' F. with Mole Fraction Ethane a8 Followe: 0.3313 0.5132 0.8763 671.10 671.03 671.17 48.91 48.84 48.78 24.238 24.174 24.113 16.021 15.960 15.897 11.910 11.859 11.798 9.402 9.348 9.460 7.502 7.396 7.447 6.202 6.162 6.104 5.279 5.235 5.192 4.594 4.552 4.515 4,029 4.064 3.998 3.644 3.616 3.692

539.21 38.73 18.877 12.266 8.961 6.989 5.410 4.386 3.657 3.126 2.727 2.4202 2.1835 1.9991 1.7312 1.5531 1.4268 1.3354 1.2121 1.1305 1.0719 1.0281 0.9923

0.8280 670.96 48.70 24.041 15.880 11.734 9,286 7.338 6,048 5.141 4.471 3.962 3.563

absolute (g). The balance was sensitive to pressure changes of 0.1 pound per square inch. The uncertainty in pressure measurement is estimated to be less than 0.1%. The experimental procedure consisted in compressing to 10,000 pounds per square inch the mixture under consideration and permitting several hours to elapse for the attainment of thermal equilibrium before making the first observation. Then, while isothermal conditions were maintained, a series of 15 or 20 volumes wa3 measured at arbitrarily chosen pressures ranging from maximum to approximately 800 pounds per square inch. Observations were taken a t 30-minute intervals with the system continuously agitated by a magnetically driven impeller within the equilibrium cell. This process was repeated for each of the seven temperatures experimentally studied. Thus, for the system of five mixtures more than six hundred equilibrium states were observed. RESULTS

Molal volumes and compressibility factors were computed from the experimental data and plotted against pressure on 50 X 75 cm. sheets of millimeter coordinate paper. Smooth curves were drawn through the isothermal points, and values at even pressures were obtained by interpolation. The results are

Vol. 37, No. 7

Pressure, Lb./Sq. In. Aba. 2,750 3,000 3,500 4,000 4,500 5,000 6,000 7,000 8,000 9,000 10,000

-

0.1777 3.299 3.020 2.592 2,2837 2.0601 1.8716 1.6157 1.4491 1.3300 1,2398 1,1683

I

0.3313 0.5132 340' F. 583.22 583.14 42.15 42.07 20.701 20.615 13,556 13.471 9.988 9.906 7.884 7.779 0.157 6.085 5.033 4.968 4.242 4.185 3.657 3.609 3.212 3.173 2.865 2,836 2.589 2.568 2.3681 2.3576 2.0387 2.0455 1.8141 1.8289 1.6497 1.6758 1.5240 1.5609 1.3559 1.4005 1.2475 1.2986 1.1699 1.2233 1.1121 1.1658 1.0669 1,1190

c

627.26 45.59 22.530 14.845 11.001 8.703 6.870 5.656 4.791 4.150 3.656 3.267 2.955 2.701 2.3121 2.0369 1.8338 1.6792 1.4650 1.3233 1.2248 1.1512 1.0931

627.20 45.54 22,480 14.797 10 965 8.667 6.841 5.631 4.777 4.141 3.654 3.271 2.964 2.714 2.3340 2.0841 1.8684 1.7194 1.5083 1.3689 1.2720 1.2000 1.1436 I

-

0.6763 0.8280 583.05 41.98 20.522 13.381 9.818 7.690 6.001 4.892 4.116 3.550 3.123 2,794 2.539 2.3352 2.0372 1.8321 1.6873 1,5810 I.4327 1.3321 1.2009 1.2059 1.1626

582.95 41.87 20.424 13.281 9.722 7.602 5.918 4.819 4.050 3.496 3.073 2.753 2.502 2.3069 2.0293 1.8441 1.7069 1.6049 1.4656 1,3691 1.2987 1.2458 1.2036

400' F. 627.13 627.05 45.46 45.38 22,406 22.325 14.728 14.654 10.896 10.823 8.607 8.534 6.784 6.717 5.579 5.515 4.726 4.668 4.096 4.046 3.616 3.574 3.241 3.206 2.942 2.914 2.700 2.076 2.3358 2.3247 2.0780 2.0766 1.8889 1.8944 1.7467 1.7585 1.5472 1.5721 1.4161 1.4469 1,3225 1.3576 1.2613 1.2898 1.1945 1.2363

626.97 45.30 22.244 14.571 10.744 8.460 6.647 6.453 4.017 4.000 3.533 3.174 2.888 2.659 2.3182 2.0828 1.9119 1.7825 1.6017 1.4838 1,3962 1.3292 1.2773

Molal Volume at 460' F. with Mole Fraotion Ethane as Follows: 0.3313 0.5132 0.8763 3.307 3.286 3.264 3.010 3.032 3.000 2.606 2.599 2.609 2.3131 2.3143 2.3047 2.0979 2.1034 2.0791 1.9336 1.9428 1.9037 1.6983 1.7162 1.6620 1.6392 1.4969 1 * 5658 1 ,4260 1.4576 1.3787 1.2924 1.3771 1,3416 1.2251 1.3134 1.2760

-

0.8286 3.243 2.987 2.598 2.3247 2.1234 1,9675 1.7473 1.5997 1.4958 1.4179 1.3578

presented as compressibility factors in Table I and molal volumes inTableII. I n the tabulation of compreasibility factors at 100' F. the density of the data a t pressures between lo00 and 2000 pounds per square inch hag been augmented in order to facilitate reconstruction of the compressibility-pressure isotherms in the region where curvature is greatest. The following numerical constants were employed in the calculations: molecular weight of carbon dioxide, 44.010; of ethane, 30.069; universal gas constant, 10.732 (pounds per square inch) (cubic feet per pound mole) per "Rankine; and absolute zero of thermodynamic tempereture, -459.69' F. The comprwibility factor wm assumed to approach the value unity at infinite attenuation of the system, and for finite volumes it wag computed from the relation:

2 = PV/RT where P = pressure, Ib./sq. in. abs. R = universal gas constant T = thermodynamic temperature, V molal volume, cu. ft./lb. mole 2 = compressibility factor

R.

The consistency of the results was tested by crom plotting values from the smooth curves with respect to composition. The isobaric-isothermal curves of volume us. composition were

INDUSTRIAL AND ENGINEERING CHEMISTRY

July, 1945

found to extrapolate nicely to the limiting values representing the volumetric behavior of the pure components. For the volumetric behavior of pure carbon dioxide the data of Michels and Michels were used (4, 6). The volumetric properties of pure ethane were obtained from data published by Beattie, Su, and Simard (1) and from the results of a recent investigation by the authors (7). The scales used in plotting the data were carefully chosen so as to permit a precision of at least 0.1% in smoothing and interpolating. A thorough graphical exmination of the experimental results indicates that the reported volumetric data are descriptive of actuality with an uncertainty probably not exceeding 0.5%. Figure 1 shows the relation between the compressibility

691

I*

I.‘

3.0

a

25

9

@ E 3

a

2.0

t

j

3

Figure 1. Compressibility Factor for Mixtures of Ethane and Carbon Dioxide at 160’ F.

1.5

+ Figure 2. Molal Volume of Ethane-Carbon Dioxide System at 100” F.

viatea most widely from that of an ideal mixture in the region of high concentrations of carbon dioxide, and these deviations become increasingly large &s the critical temperatures and pressures of the components are approached.

I .o

ACKNOWLEDGMENT 05

02

OA 06 WXC TRACTION LTHANE

08

factor and preasure at 160’ F. for the pure components and the five experimentally studied mixturea. The experimental valuea are represented by circlee, and the curves are drawn in mcordance with the final smoothed results obtained by or088 plotting the experimental data with respect to temperature and composition. lt may be noted that the minimum values of the compressibility factor of the pure components are lees than those Of the mixtures, and the curves of the family describe a saddle-shaped surface in the neighborhood of their minima. Figure 2 gives ieobaric curves relating mold volume and molal composition at 100’ F. For the moat part each of these curvea lies above a straight fine joining ita extremities. This indicates that, in general, the mixing of the componente under isobaric, isothermal conditions results in a total volume which is greater than the sum of the volumes of the components before mixing. In fact, Figure 2 shows that the actual volume of 8. mixture may exceed that predicted on the basis of ideal mixtures by aa much

aa 20%. As in the case of the methane-carbon dioxide system (6) the volumetric behavior of the ethane-carbon dioxide system de-

Thiswork represents part of the activities of Research Projeot 37 of the American Petroleum Institute. The financial support and encouragement of that organiration are gratefully acknowledged. The cooperation of H. A. Taylor and E. S. Turner in connection with the experimental operations and the assistance of Louise Reaney in the calculations and preparation of figures are appreciated. 1.0

LITERATURE CITED

(1) (2) (3) (4)

Beattie, Su, and Simmd, J . Am. C h m , &c,, 61, 926 (1939). Bridgemm, I b a . , 49, 1174 (1927). Callendar, Trans. Roy. SOC.(London), 178, 160 (1887). Michele and Michela, Proc. Roy. 8oc. (London), A153, 201

(6) Ibid., (1936). AIBO, 348 (1937). (6) Reamer, Olds, Sage, and Lacey, IND.ENQ.CEEM.,36,88 (1944). (7) Ibid., 38,966 (1944). (8) Sage and Laow, Tram. Am. Inst. Mining Met. Ewrs., 136, 136

sander, (1940). I,physikil;. chsnt., A78, 813 (1912). (io) Smith and Keyes, Proc. Am. Amd. Ark Sci., 69, No. 7, 314 (1934). (11) Wan and Dodge, IND.ENQ.CHEM., 32,96 (1940). pAPER 46 in the series “Phrsae Equilibria in Hydrocarbon Syatenls”. previous artiales have appeared during 193440 and 1942-44, inclusive.