Phase Equilibria in Hydrocarbon Systems J
J
Joule-Thomson Coefficients in the Methane-Propane System'
Joule-Thomson coefficients of three mixtures of methane and propane were determined experimentally at pressures up to 1500 pounds per square inch in the temperature interval between 70' and 310' F. From these experimental data and published heat capacity values for the components at infinite volume, the isothermal enthalpy-pressure coefficients were calculated. From these derived values the partial enthalpies of methane and propane in mixtures of the two substances were established. The results are presented in graphical and tabular form.
R. A. BUDENHOLZERz, D. F. BOTKIN, B. H. SAGE, AND W. N. LACEY California Institute of Technology, Pasadena, Calif.
,'
I
NFORMATION concerning the volumetric and thermodynamic behavior of binary gaseous hydrocarbon mixtures is of direct value in estimating the influence of the components upon the properties of the multicomponent gaseous mixtures encountered in practice. Joule-Thomson coefficients are useful in determining the influence of temperature upon the specific volume as well as the influence of pressure upon the heat capacity and enthalpy of the fluid in question. These coefficients are of special value a t relatively low pressures where the evaluation of the quantities enumerated above from volumetric measurements involves the small difference between two relatively large quantities and requires very high experimental precision. Published exDerimenta1 work relating to the behavior of mixtures of me'thane and propane a t elevated pressures is limited t o a single preliminary investigation (16) of the volumetric and phase behavior of this system. These data were not of sufficient accuracy in the singlephase region to permit the isothermal changes in i enthalpy and in heat capacity to be ascertained with certainty. The influence of composition upon the volust metric behavior of this system was sufficiently ina W complete to make necessary some additional work before the prediction of the partial behavior (9) of m propane might be made with an accuracy comparable to that for the other lighter paraffin hydrocarbons. However, it is believed that the phase behavior in this system was determined in enough detail to suffice t for present needs even though it is subject to somewhat larger uncertainties than those for more recently studied binary mixtures. Joule-Thomson coefficients for pure methane were reported (3) over the greater part of the range of temperatures and pressures currently investigated. From these data and values of the isobaric heat capacity a t infinite volume, based upon spectroscopic measurements ( I @ , the heat Y
capacity and enthalpy for methane a t elevated pressures were computed ( 3 ) . Similar information is available (IS) for propane throughout the gaseous region a t pressures below 550 pounds per square inch in the temperature interval between 70" and 220" F. Recently the volumetric behavior of gaseous propane was studied in some detail by Beattie and co-workers ( I , 2 ) . These measurements were combined by Nellis with more recent studies made a t this laboratory ( I O ) , and the results have been used as the basis of the thermodynamic properties of propane utilized in this work.
Method Experimental measurements of the Joule-Thomson coefficients of mixtures of methane and propane were made at five systematically chosen temperatures between 70" and 310" F. for pressures up to 1500 pounds per square inch. The apparatus and methods employed in this work have
5 L 2 50
1
I
I
I
500
7 50
1000
I250
PRESSURE
This is the thirty-fourth paper in this aeries. Previous articles appeared during 1934-1940, inclusive. and in June, 1940 ( 1 6 ) . f Present address, Illinois Institute of Technology, Chicago. Ill. 1
I
LE. P E R SQ. IN.
FIGURE1. JOULE-THOMSON COEFFICIENT FOR A MIXTURECONTAIKING 0.7552 WEIGHT FRACTION METHANE 818
INDUSTRIAL A N D ENGINEERING CHEMISTRY
July, 1942
TABLE I. JOULE-THOMSON COEFFICIENTS' AND ISOBARIC HEAT FOR GASEOUS MIXTURES OF METHANE AND PROPANP CAPACITIES~ In. 0 200 400 600 800 1000 1250 1500
Fraction Methane as Follows:4.49344.7552P CP P CP 0.1288 0,4311 0.0916 0.4636 0.0675 0.4980 0.1430 0.4899 0.0939 0.5058 0.0694 0.5286 0.0935 0.5580 0.0698 0.5660 0.0905 0.6286 0.0691 0.6096 . . 0.0678 0.6598 , 0.0660 0.7170 . 0.0633 0.7997 .. 0.0604 0.8998
0 200 400 600 800 1000 1250 1500
0.1066 0.4425 0.0780 0.4744 0.0590 0.1262 0,4908 0.0807 0.5066 0.0605 0.1339 0.5571 0.0801 0.5456 0.0610 0.0775 0.5932 0.0606 0.1295 0.0727 0.6531 0.0595 0.0650 0.7228 0.0578 0.0553 0.8207 0.0552 0.0460 0.0519
.... .... .... .. ..
.... .... .... .... .. . .
0.5081 0.6319 0.5605 0.5934 0.6317 0.6758 0.7404 0.8173
0 200 400 600 800 1000 1250 1500
0.0939 0.1100 0.1156 0.1169
0.4539 0,4936 0.5519 0.6263
.... .... ..
.... ,... .... ....
0.0692 0.0716 0.0713 0.0693 0.0653 0.0601 0.0526 0.0452
0.4855 0.5111 0.5413 0.5759 0.6137 0.6527 0.6998 0.7415
0.0520 0.0534 0.0540 0.0536 0.0525 0.0509 0.0483 0.0448
0.5189 0.5379 0.5593 0.5840 0.6128 0.6462 0 6949 0.7512
0 200 400 600 800 1000 1250 1500
0.0834 0.0944 0.0991 0.0994 0.0953 0.0827
0.4654 0.4981 0,5485 0.6138 0,6880 0.7566
....
0.0611 0.0634 0.0634 0.0619 0.0587 0.0552 0.0496 0.0438
0.4971 0.5179 0.5421 0.5683 0.5956 0.6233 0.6558 0,6836
0.0464 0.0477 0.0482 0.0479 0.0466 0,0446 0.0422 0.0389
0.5305 0.5463 0.5637 0.5828 0.6045 0.6299 0.6666 0.7087
190
0 200 400 600 800 1000 1250 1500
0.0746 0.0812 0.0846 0.0852 0.0822 0.0751 0.0619 0.0480
0.4774 0.5048 0.5474 0.6031 0.6669 0.7278 0.7719 0.7759
0.0544 0.0562 0.0566 0.0554 0.0532 0.0505 0.0462 0.0416
0.5092 0.5271 0.5474 0.5688 0.5906 0.6118 0.6371 0.6588
0.0414 0.0428 0.0436 0.0428 0.0414 0.0394 0.0370 0.0342
0.5428 0.5564 0.5710 0.5869 0.6046 0.6240 0.6510 0.6808
220
0 200 400 600 800 1000 1250 1500
0.0666 0.0706 0.0726 0.0732 0.0716 0.0678 0.0598 0.0514
0.4898 0.5134 0.5472 0.5905 0.6413 0.6927 0.7397 0.7523
0.0487 0.0501 0.0504 0.0496 0.0480 0.0461 0.0426 0.0388
0.5219 0.5379 0.5556 0.5740 0.5926 0,6106 0.6316 0.6506
0.0370 0.0386 0.0390 0.0384 0.0370 0.0352 0.0328 0.0302
0.5558 0.6682 0.5810 0.5944 0.6086 0.6234 0.6429 0.6642
0 200 400 600 800 1000 1250 1500
0.0595 0.0618 0.0632 0.0637 0.0632 0.0612 0.0572 0.0525
0.5021 0.5233 0.5497 0.5819 0.6196 0.6597 0.7024 0.7265
0.0438 0.0448 0.0451 0,0445 0.0432 0.0417 0.0387 0.0356
0.5347 0.5491 0.5649 0.5815 0.5981 0.6145 0.6340 0.6518
0.0330 0.0346 0.0348 0.0344 0.0332 0.0316 0.0293 0.0269
0.5692 0.5806 0.5924 0.6044 0.6166 0.6288 0.6446 0.6611
0 200 400 600 800 1000 1250 1500
0.0529 0.0543 0.0557 0.0561 0.0557 0.0551 0.0536 0.0502
0.5144 0.5336 0.5552 0.5797 0,6077 0.6379 0.6751 0.7079
0.0392 0.0399 0.0401 0.0397 0.0387 0.0374 0.0348 0.0320
0.5476 0.5611 0.5755 0,5909 0 6063 0.6215 0.6400 0.6578
0.0295 0.0311 0.0316 0.0310 0.0300 0.0285 0.0263 0.0241
0.5827 0.5933 0.6041 0.6151 0.6261 0.6371 0.6506 0.6641
0 200 400 600 800 1000 1250 1500
0.0461 0.0480 0.0492 0.0498 0.0498 0.0492 0.0477 0.0453
0,5270 0.5450 0.5635 0.5833 0.6049 0.6280 0,6598 0.6951
0.0348 0.0355 0.0356 0.0352 0.0344 0.0332 0.0308 0.0284
0.5608 0.5734 0.5866 0.6010 0.6154 0.6296 0.6%73 0.6649
0.0264 0.0278 0.0283 0.0280 0.0270 0.0257 0.0238 0.0217
0.5965 0.6063 0.6163 0.6265 0.6367. 0.6469 0.6594 0.6719
Temp., F. 70
100
130
160
250
280
310
Pressure
Lb./Sa:
-Weight 4.2458P
CP
....
.... .... .. .. ........ ....
.... .. .. . ......
....
....
....
,...
.. .... .. ........
........ ... ,.. .
. .. .
I
already been described (S), and it was not necessary to modify the equipment in any essential detail. It is believed that the average temperature was determined within 0.1' F. relative to the international platinum scale, while uncertainties in the average pressures for the measurements larger than 1 pound per square inch are unlikely. The pressure difference was determined from the indication of a calibrated mercury-in-steel manometer and was established within 0.2 per cent, while the temperature difference was measured by means of a four-junction, multilead, copper-
879
constantan thermocouple. The thermocouple was calibrated against a strain-free platinum resistance thermometer which had been standardized a t the National Bureau of Standards. However, difiiculties in maintenance of steady flow conditions through the porous thimble resulted in an uncertainty of approximately 2 per cent in the evaluation of the JouleThomson coefficient from the measured temperature and pressure differences. Throughout this work a pressure difference of approximately 12 pounds per square inch was employed. The values of the coefficient are reported for the average of the pressures and temperatures on the two sides of the thimble.
Materials The methane utilized was obtained from the Buttonwillow gas field in California. Condensation analyses upon the material as received have shown that it contains less than 0.0003 mole fraction of hydrocarbons of greater molecular weight than methane and approximately 0.003 mole fraction of carbon dioxide. Before use this gas was passed at elevated pressures through granular beds of calcium chloride, potassium hydroxide, activated charcoal, and magnesium perchlorate in order to remove the water, carbon dioxide, and heavier hydrocarbons. It is believed that the methane actually employed contained less than 0.0001 mole fraction of impurities. The propane was procured from the Phillips Petroleum Company with a special analysis indicating that it contained less than 0.0003 mole fraction of material other than propane. This hydrocarbon was utilized without further purification. Prior to use the mixtures were prepared in suitable steel pressure vessels, and the composition was ascertained from precision gas density measurements at 100' F. and atmospheric pressure. It is believed that the uncertainty in the mole fractions of the components in the mixture at the time of sampling was less than 0.001. However, during the course of a set of measurements there was a tendency for the material to become progressively richer in methane. Several samples of the material in the apparatus were taken at each temperature, and it was found that variations of as
a2
0.4
WEIGHT
FRACTION
0.6
0.8
1.0
METHANE
OF COMPOSITION ON JOULE-THOMSON FIQURE2. INFLUENCE COEFFICIENT IN METHANE-PROPANE SYSTEMAT 250' F.
880
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
much as 0.01 in the mole fraction were obtained in cases involving mixtures rich in propane. These variations in composition were taken into account in the graphical interpolation of the results. I n general, it is believed that t.he uncertainties resulting from variation in the composition of the material under investigation were much smaller than those introduced in the measurements of the Joule-Thomson coefficient.
Vol. 34, No. 7
0.9
$
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4
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a
Experimental Results
0.7
3
2
A typical set of experimental results for a mixture rich in methane is presented in u" 0.8 Figure 1. The general trends in these data .are similar to those encountered in other studies of binary paraffin hydrocarbon mixtures (4, 6). The Joule-Thomson coeffi0.5 dents graphically interpolated to even values of pressure for the experimentally studied mixtures are recorded in Table I. It is believed that the uncertainty in these tabulated data is not more than 2 per cent except at states in the immediate vicinity of the heterogeneous region where it beF I G U R E 3. comes somewhat larger. The influence of comnosition unon the Joule-Thomson coefficient i n t h i s b i n a r y s y s t e m a t 250" F. is indicated in Figure 2. The data corresponding to zero pressure have been extended to a composition corresponding to pure propane. Similarly the curves for pressures of 1250 and 1500 pounds per square inch have been indicated throughout the enti& composition interval. The latter curves have been dotted a t compositions containing less than 0.2 weight fraction methane since ~~~~~
ENTHALPIES OF METHANE IN TABLE 11. PARTIAL Pressure, Lb./Sq. In. Abs.
c
70°F.
1OOOF.
5.3 3.1
0 200 400
21.3 19.2 16.8
3.0
600
..
..
800
1000
..
1250 1500
0
200 400 600 800 1000 1250 1500
5.3 0.2 5.2 -10.8
-
..
.. ..
21.3 16.7 11.9 6.8 - 41..84
..
0 200 400 600 800 1000 1250 1500
6.3 0.2 6.0 -12.0 -18.2 -24.6 -32.7 -41.1
21.3 16.4 11.2 5.9 0.4 - 5.2 -12.5 -20 2
0
5.3 0.2 - 5.9 -13.0 -21.0 -28.8 -36.4 -43.7
21.3 16.2
200 400
600
800 1000
1250 1500
-
-
11.1 5 6 0.2 5.1
-11.8 -16.2
THE
I
i
I
500
1000 PRESSURE
ISOBARIC
HEATCAPACITY FOR A &XTURE %'EIGHT FRACTION hh'HAtiE
280OF.
310'F.
0.4 Weight Fraction Methane 37.7 54.4 71.4 66.8 35.7 52.2 69.2 86.4 35.1 51.4 07.9 64.5 35.4 51.5 07.5 83.3 52.2 68.1 82.9 .. 53.6 69.1 63.2 .. 70.1 83.9 .. .. 69.0 84.8
106.7 104.3 102.2 100.5 99.4 98.9 99.2 100.7
124.9 122.6 120.5 118.6 117.0 116.0 115.4 115.7
143.6 141.4 139.4 137.6 136.6 136.0 136.0 136.7
0 . 6 Weight Fraction Methane 37.7 54.4 71.4 88.8 33.6 50.6 67.8 85.6 29.3 46.6 64.1 82.2 24.8 42.5 60 3 76.7 20.0 38.1 56.5 75.3 14.6 33.6 52.7 72.0 7.1 27.5 47.8 68.0 21.0 42.9 64.3
106.7 103.7 100.6 97.6 94.6 91.7 86.2 84.9
124.9 122.0 119.0 116.0 113.1 110.3 107.0 104.0
143.6 141.0 138.3 135.4 132.7 130.1 127.2 124.5
0 . 8 Weight Fraction Methane 37.7 54.4 71.4 88.8 33.3 50.3 67.7 85.4 28.6 46.1 63.8 81.9 23.6 41.7 59.9 78.2 19.0 37 4 55.9 74.6 14.1 32.9 52.0 71.1 7.8 27.3 47.3 66.8 1.3 21.7 42.8 62.6
106.7 103.5 100.3 97.0 93.7 90.5 86.6 82.9
124.9 122.0 119.0
112.9 110.0 106.4 102.9
143.6 140.9 138.1 135.3 132.5 129.7 126.4 123.4
1 .O Weight Fraction AIethane 37.7 54.4 71.4 88.8 33.0 50.1 67.6 85.4 28.3 48.8 63.7 61.8 23.5 41.5 59.8 76.2 18.8 37.1 55.8 74.6 14.1 33.1 52.0 71.2 8.3 27.9 47.4 67.0 2.7 23.0 42.9 63.0
106.7 103.6 100.2 97.0 93.8 90.7 86.9 63.2
124.9 122.0 119.0 116.0 113.0 110.0 106.4 102.8
143.6 140.9 138.2 135.4 132.7 130.0 126.7 123.5
..
0.7652
Derived Quantities
Partial Enthalpy, B. t. u. per pound 130'F. l6O'F 190'F. 220OF. 250'F.
..
CONTAIPiING
the behavior in this region was not established in detail. The indicated values of the Joule-Thomson coefficients for propane were computed from available thermodynamic d a t i (10).
METHASE-PROPANE SYSTEM
..
1500
Le. PER Sp. IN.
116.0
In accordance with method3 described ( I S ) , the heat capacities of the mixtures investigated 1%-erecalculated as a function of state. Spectroscopic measurements for methane (18) and isentropic temperaturepressure coefficients for propane (17) were employed in connection with the behavior of ideal solutions (8) to establish the heat capacity a t infinite volume throughout the temperature range of interest, probably within 1.5 per cent. The values of the isobaric heat capacity a t elevated pressures are recorded in Table I. These data probably do not involve uncertainties greater than 2.5 per cent, except at states in proximity to the two-phase region. The isobaric heat capacity of a mixture containing 0.7552 weight fraction methane is depicted as a function of pressure in Figure 3 for each of the temperatures investigated. A more rapid increase in the heat capacity with pressure a t the lower temperatures causes the somewhat complicated behavior indicated. However, this is in accord with results obtained for other gaseous hydrocarbon mixtures. The influence of composition upon the isobaric heat capacity a t
INDUSTRIAL AND ENGINEERING CHEMISTRY
July, 1942
881
The application of this equation to the results recorded in Table I for Pressure the mixture containing 0.7552 weight c Partial Enthalpy, B. t. u. per pound Lb./Sq.' fraction methane yields the values of 7OoF. 100'F. 130'F. 160'F. 19OOF. 220 F. 250'F. In. Abs. 280'F. 310'F. the isothermal enthalpy-pressure coef0 Weight Fraction Propane ficient depicted in Figure 5 . These 16.1 28.6 41.5 54.7 68.3 82.2 96.5 111.2 4.0 0 results are in accord with those found 19.9 33.4 47.0 61.5 76.1 90.5 106.2 200 - 7 . 7 - 64 .. 81 10.5 24.8 39.0 54.4 400 69.7 84.1 100.6 for other gaseous hydrocarbcn mix15.8 30.7 47.1 -16.8 0.3 63.1 77.6 - 20.6 35.1 94.8 600 22.3 39.9 -30.2 -10.7 800 51.2 6.2 56.6 71.2 88.9 tures. -23.1 13.9 32.6 -45.3 - 4.1 50.1 65.2 83.3 1000 - 69.6 The prediction of the enthalpy of -68.1 -40.9 -18.1 3.5 23.9 1250 42.5 58.2 77.1 ... -98.1 -61.9 -33.2 - 6 . 8 15.8 35.4 51.9 72.1 1500 ... gaseous hydrocarbon mixtures is im0 . 2 Weight Fraction Propane portant in certain engineering opera82.2 96.5 111.2 tions. The isothermal changes in 16.1 28.6 41.5 54.7 68.3 0 4.0 33.2 46.8 61.4 19.6 200 - 8 . 0 - 5.9 76.0 90.5 106.0 enthalpy of the pure hydrocarbons 24.5 38.7 54.1 9 . 9 5 . 3 69.4 84.5 100.6 400 - 21.2 15.3 30.4 46.7 - 0.6 600 - 36.1 62.7 78.3 95.1 were correlated on the basis of the 22.1 -30.7 -11.8 5.9 39.2 800 - 52.6 -17.5 56.1 72.1 89.5 law of corresponding states by York 13.7 -44.9 -23.4 3.6 31.9 1000 70.8 49.6 66.1 84.0 -38.1 -15.3 23.0 1250 - 95.6 -63.4 3.4 58.8 77.5 and Weber (IO),and this method ap-82.5 -52.9 -26.4 1500 -122.8 - 6 . 4 14.4 41.8 34.5 82.2 71.7 parently yields results of reasonable 0.4 Weight Fraction Propane accuracy. Attempts to extend the 16.1 28.6 41.5 54.7 68.3 0 82.2 96.5 111.2 method, in conjunction with the values 5.6 18.9 32.9 46.9 61.1 200 - 84.0 .7 75.6 90.6 105.8 - 6.1 8.3 23.7 38.6 53.5 400 - 22.9 68.6 84.6 100.4 presented by Edmister (6), to niix-18.6 --132 . 77 14.1 30.0 45.8 600 - 38.6 -31.6 61.5 78.4 94.8 tures on the basis of the pseudocriti4.5 21.4 37.9 800 55.9 54.2 72.2 89.3 -44.4 -24.2 - 4.9 12.8 30.1 ... 1000 47.0 65.8 83.7 cal concept of Kay (7) did not yield 1250 ... -59.0 -35.8 -15.8 2.6 20.6 38.2 58.0 76.7 .. - 4 5 . 1 -25.3 - 6 . 6 1 1 . 8 29.9 50.5 1500 ... 70.0 values (15) with as small an uncertainty as might be desired. For this 0 . 6 Weight Fraction Propane reason the use of partial enthalpies (9) 16.1 28.6 41.5 0 4.0 54.7 68.3 82.2 96.5 111.2 3.2 17.3 31.0 200 - 11.6 -12.3 45.7 60.2 74.6 90.0 105.4 appears to be of even greater value 400 3.8 18.8 35.2 - 30.3 51.2 66.0 83.2 99.2 in the prediction of the enthalpies of 600 .. -11.2 5.5 23.2 41.4 ... 56.6 75.9 92.7 .. 800 ... .. - 8.4 1 0 . 1 30.8 46.2 68.3 85.8 gaseous hydrocarbon mixtures than .. .. -22.7 3.1 19.9 ' 1000 ... 35.2 60.4 78.5 .. 1250 ... .. *. -17.9 6.4 21.2 50.0 68.7 does the use of partial volumes in the .. 1500 .. .. -29.9 - 5 . 9 7.5 39.3 58.2 prediction of the volumetric behavior bf these materials. The partial e n t h a l p y - p r e s s u r e coefficients were computed from 250" F. is shown in Figure 4. The results have not been values of the enthalpy-pressure coefficient for the mixextended to compositions rich in propane in all cases because tures studied experimentally and for the pure components of uncertainty as to the details of behavior in this region. by application of the method of Roozeboom (11). From The isothermal enthalpy-pressure coefficient is related the partial enthalpy-pressure coefficients and information to the Joule-Thomson coefficient and the isobaric heat concerning the heat capacities of the components (17, 18), capacity in the following way: the partial enthalpies of methane and propane in the methanepropane system were established. An arbitrary datum at 60" F. and infinite volume was employed for each of these PCP = materials. The partial enthalpies of methane and propane are recorded as functions of temperature, pressure, and composition in Tables I1and 111. Uncertainties o rs greater than 1.5B. t. u. in the tabulated values are unlikely. Comparison of the behavior of meth010 ane in the methane-ethane ( 1 4 , methane-12-butane ( l a ) , and methane-n-pentane (15) systems w t h 0.65 the values recorded in Table I1 ina dicates a rather complex variation 0 2 in the behavior of this hydrocaraeo bon with variation in the molecun lar weight of the heavier com0 ponent. ass TABLE 111. PARTIAL ENTHALPIES ,OFPROPANE IN THE METHANE-PROPANE SYSTEM 7
I . .
(g)T
$
Acknowledgment
WEIOCIT
FRACTION
YETHAUL
FIGURE 4. INFLUENCE OF COMPO~~ITION ON ISOBARIC HEATCAPACITY IN METHANEPROPANE SYSTEM AT 250" F.
This work was carried out as a part of the activities of Research Project No. 37 of the American Petroleum Institute. Cooperation and financial support from the Institute made this work possible. The assista n c e of L . F a y P r e s c o t t i s
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
882
VOl. 34, NO. ’I
Literature Cited (1) Beattie, Kay, and Kaminsky, J . Am. Chem. Soc., 59, 1509 (1937). (2) Beattie, Poffenberger, and Hadlock, J . Chem. Phys., 3, 96 (1935). (3) Budenholzer, Sage, and Lacey, IND. EN@. CHEM., 31, 369 (1939). (4) Ibid., 31, 1288 (1939). (5) Ibid., 32, 384 (1940). (6) Edmister, Ibid., 30, 352 (1938). (7) Kay, Ibid., 28, 1014 (1936). (8) Lewis, J . A n . Chem. SOC., 30, 668 (1908). A m . Acad. Sci., (9) Lewis, PTOC. (1907).
I
I 250
500
150
PRESSURE
I000
I
1
1250
1500
43, 273
(10) Nellis, Calif. Inst. of Tech., master’s thesis, 1938. (11) Roozeboom, “Die heterogenen Gleichgewichte”, Vol. 11, part 1, p. 288 (1904); Lewis and Randall, “Thermodynamics”, p. 38. New York, McGraw-Hill Book Co., 1923. (12) Sage, Budenholzer, and Lacey, IND. ENG.CHEM.,32, 1262 (1940). (13) Sage, Kennedy, and Lacey, Ibid., 28, 601 (1936).
LE. PER Sa. IN.
FIQURE5. ISOTHERMAL ENTHALPY-PRESSURE COEFFICIEKT FOR CONTAINING 0.7552 WEIGHT FRACTION METHANE
A
MIXTURE
(14) Sage and Lacey, Ibid., 31, 1497 (1939). (15) Ibid., 34, 730 (1942). (16) Sage, Lacey, and Schaafsma, Ibid., 26, 214 (1934). . ,
(17) Sage, Webster, and Lacey, Ibid., 29, 1309 (1937).
acknowledged in connection with the calculation of the heat capacities and of the partial enthalpies.
(18) Vold, J . Am. Chem. SOC., 57,1192(1935). . , 388 (1940). (19) York and Weber, IND.ENG.C H ~ M32,
Viscositv of Naphtha-Resin Solutions J
E. H. MCARDLE AND E. L. BALDESCWIELER Esso Laboratories, Standard Oil Development Company, Elizabeth, N. J.
A variation of only a few degrees in the average boiling point of a given thinner produces critically large changes i n resin solution viscosity. The average boiling point-viscosity slope of a resin solution in a hydrocarbon thinner becomes steeper with increasing homogeneity, with respect to hydrocarbon type.
I
N A PREVIOUS paper (3)attention was called to the surprisingly large increment in resin solution viscosity resulting from slight changes in the average boiling point, or average molecular weight, of a 99 per cent isoparaffinic naphtha solvent. A rise of only 9’ F. (5” C.) in average boiling point produced an increase in viscosity of 55.6 per cent, in the case of the particular alkyd resin solution studied. It was therefore decided t o extend this survey to other types of
hydrocarbons and also to include resins of a variety of molecular weights. A series of resins was accordingly obtained ranging in average molecular weight from that of ester gum (a monomer-dimer mixture) to that of an alkyd with high glycerol phthalate content; and two groups of naphthas were assembled as base stocks. One group included a series of three blends, respectively, of paraffins, naphthenes, and aromatics of high purity; the other was chosen from representative commercial thinners. Each pure hydrocarbon blende. g., normal paraffins-and each commercial thinner was then fractionated into a series of five naphthas whose average boiling points differed by only a degree or two. Except for the pure naphthenes and pure aromatics, all naphtha fractions lie in the mineral-spirits boiling range.
Naphthas The normal paraffinic naphtha stock was a blend of two volumes of nonane, two volumes of decane, and one volume of undecane. These materials were obtained through the courtesy of the Petroleum Refining Laboratory of Pennsyl-
