INDUS'TKIAL A S D ENGINEEKING CHEMISTRI-
984
(3) Beilstein, F., and Kurbatow, A , Ber., 13, 1818 (1880). (4) Bestuschew, M., Erddl u. Teer, 7 , 1 9 2 (1931). (5) Bingham, "Fluidity and Plasticity," 1st ed., S e w Tork, McGraw-Hill Book Co., 1922. (6) Braun, J. von, Allgem. Oel- u. Felt-Ztg., 25, XneralbZe, 1, 13-14 (1930). (7) Brooks, B. T., and Humphreys, I. W., J . Am. Chem. Soc., 38, 397 11916). (8) Ibid., 40, 822 (1918). (9) Bruun, J. H., and Hicks-Bruun, hI. M., Bur. Standards J . Research, 10,465 (1933). (10) Carpenter, J. h.,J . Inst. Petroleum Tech., 12, 518 (1926). (11) Davis, G. H. B., Lapeyrouse, M., and Dean, E. W,, Oil Gas J . , 30. No. 46. 92 (1932). (12) Davis, G. H . B., and Mcdllister, E. N,, ISD ESG. CHELI.,22, 1326 (1930). (13) Dean, E. IT., and Davis, G. H. B., Che7n. & M e t . Eng., 36, 618 (1929). (14) Dunst'an, A. E., and Thole, F. B., J . Inst. Petroleum Tech., 4 , 204 (1917). (15) Engler, C., 2. angew. Chem., 1888,73. (16) Garner, F. H., and Kelly, C. I.,Physics, 4 , 97 (1933). (17) Glazebrook, R . T . , Higains, TT., and Parnell, J. R., J . Insf. Petroleum Tech., 2, 64 (1916). (18) Herschel, IT. H., Proc. A m . SOC.Testing Materials, 21, 363 (1921). (19) Ibid., 22, Part I, 423 (1922). (20) Hugel, G . , Chimie & Industrie, 26, 1282 (1932). (21) Landa, S., Cech, J., and Sliva, T., Collection CtechosloE. Chem. Comnzzcnications, 5, 204 (1933). (22) Lerer, M.M . , Ann. comb~astiblesliq~aides, 8, 681 (1933). (23) Jlabery, C. F., Am. Chem. J.,19,419 (1897).
I'OL. 28, NO. 8
(24) Mabery, C . F., IND.ENG.CHEY., 15, 1233 (1923). (25) Mabery, C. F., J . Am. Chem. Soc., 48, 2663 (1926); 49, 1116 (1927). (26) Mabery, C. F., and Mathews, J. H.,Ibid., 30,992 (1908). (27) Marcusson, J., Chem.-Ztg., 37, 533, 550 (1913). (28) Markownikoff, W., and Oglobin, W.,Bull. soc. chim., 41, 268 (1884). (29) Markon-nikoff, W., and Oglobin, IT., J . RUSS. Physik. Chem. Ges., 1883 (7), 237, 307; Ber., 16, 1873 (1883). and Spady, J.. Ber., 20, 1850 (1887). (30) Markownikoff, W., (31) Oelschla-cer. E.. 2. V e r . deut. I n a . . 6 2 . 4 2 2 (19181. (32) Pelouxe,>., and Cahours, A , , 60mpt. r e d , 54, 1241 (1862) ; 56, 506 (1863) : 57, 62 (1863). (33) Rue, W.de la, and Muller, H., Proc. Roy. SOC.(London), 8, 221 (1856). (34) Sachanen, A,, and Wirabianz, R., Erdol u. Teer, 9, 187 (1933); Petroleum Z., 25, 867 (1929). (35) Schneider, J., and Just, J., 2. wiss. X i k r o s k o p . , 22, 981 (1905). (36) Schorlemmer. C., Chem. S e w s , 7 , 157 (1863). (37) Schorlemmer, C., J . Chem. SOC.,15,419 (1862). (38) Spilker, -1.J . , Brennst0.f-Chem., 7, 261 (1926); 2. a n g e u , Chem., 39, 997 (1926). (39) Sulliran, F . W., Jr., Voorhees, T,,Neely, A. TT., and Shankland, R . T., ISD. ESG. CHEH.,23, 609 (1931). (40) Tlugter, J. C . , \Taterman. H . I., and Westen, H. A. van. J. Inst. Petroleum Tech., 18, 736 (1932). (41) Karren, C . >Proc. I.,A m . Acad. d r t s Sci., 27, 56 (1891). (42) Wilson, W.J., and .Illibone, B. C., J . Inst. Petroleum Tech., 1 1 , 180 (1925). (43) Zrlinsky, S . D., and Kaznnsky,B. .I., B e r . , 64, 2265 (1931).
RECEIVED .ipril 18, 1936
Publication of tables with structural formulas made possible through the codperallon and financial assistance of the Standard Oil Development Comprtny.
Phase Equilibria in Hydrocarbon Systems XV. Mixtures of Methane and B. H. SAGE, D. C. WEBSTER, AND W. N. LACEY California Institute of Technology, Pasadena, Calif.
@A
S A PART of the general study of the thermodynamic properties of naturally occurring hydrocarbon mixtures being conducted by Research Project No. 37 of the American Petroleum Institute, an experimental study of some of the mixtures of methane and a crude oil has been made. The temperature range investigated was from 70" to 220" F., and each mixture was studied a t pressures from 300 to 3000 pounds per square inch. The seyen mixtures investigated varied systematically in composition from the crude oil to mixtures containing about 10 mass per cent methane. The measurements included (a) specific volumes as a function of pressure, temperature, and composition, and (b) specific heats as a function of temperature and composition a t a given constant volume. It was not feasible to investigate the behavior of mixtures containing higher concentrations of methane than those cited above because of the separation of a second liquid phase, apparently asphaltic in character. The separation of this third phase may be due to the low solubility of asphaltic material in hydrocarbon liquids containing appreciable quantities of the lighter compounds. This additional phase rendered further measurements useless as the attainment of equilibrium was quite uncertain.
.
Previous articles in this series appeared during 1934 and 1935, and in January, February, April, May, and June, 1936
a Crude Oil'
I
I Specific volumes and speqific heats of several mixtures of methane and a crude oil from the Santa Fe Springs Field, Calif., were determined. Several diagrams illustrating the behavior of such mixtures are shown.
Materials The crude oil chosen for this x-ork was a composite sample from several of the important producing zones in the Santa Fe Springs Field of California. The same oil was used in earlier studies (7, 8). The physical properties of the oil sample were as follows: gravity, 34.9" A. P. I. a t 60" F.; specific gravity,2 0.8495 a t 60" F. and 1 atmosphere; flash point, below 80" F.; pour point, below 0" F.; viscosity, 42 seconds (Saybolt Universal) a t 100" I?.; kinematic viscosity, 4.73 centistokes a t 100" F.: water and sediment by centrifuge and by distillation, trace. 4 sample of this oil was distilled in a laboratory column to determine directly the quantity of each of the hydrocarbons from methane through pentane. The residue 2 T h e term "specific gravity" is here used t o denote the ratio of the weight of a given volume of the material a t a specified temperature and pressure to the weight oi the same volume of water a t its maximum density a t atmospheric pressure.
I\DUSTHI4 I, .L\D E\GINEERI\G
I L G L S T , 1936 AVERAGE
BOILING
POINT
985
CHE\IISTRk
'F.
100
50
0
T E MP E R AT UR E
OF.
2. SPECIFIC HEATAT COSSTIS'T SPECIFIC VOLUME OF p.035 C T B I C FOOT PER P O r S D FOR CRUDE O I L .ISD THREE h l I X T U R E s WITH M E T H . I S E
FIGURE
"
5
c Lo I
0.55
w
% 200
300 AVCRAGE
400
500
BOILING POINT
-.
600
FIGURE1, RESULTSFROM h A L T T I C A L OF CRUDE OIL
0.50
DISTILL.4TIOS
3
from this distillation was further distilled using a 0.4 5 r e c t if y i n g column containing twelve perforated plates, separate consecutive overhead fractions of approximately 5 volume per cent being collected. For each of these fractions, determinations >\-ere made of specific gravity, absolute viscosity, arer0.4 0 IO0 125 150 175 200 age molecular weight (by the freezing point lowerO F . T E MPERAT URE ing of benzene), and the average boiling point (by A. S. T. M. Engler distillation). Some of the reFIGURE3. SPECIFIC HEATBT A CONSTAST SPECIFICVOLUMEOF 0.035 CUBIC FOOT PER POUND FOR T H R E E ADDITIONIIL MIXTURES sults of this analysis are given in Table I. Figure 1 shows the average molecular weights, absolute viscosities, and specific gravities of the various fractions hydrocarbons, and the authors believe that less than 0.2 per plotted against their average boiling points. The cumulacent of nitrogen and other inert gases was present. tive mass fraction distilled is also plotted against the same abscissa. The Dentanes and lighter hvdrocarbons TTere reExperimental Results ported as part oE the first fraction in Figure 1. The apparatus and experimental methods used have been The methane used in this work was prepared hy a method previously described (3,.4,9). The volumes of the mixtures similar to that used in an earlier investigation ( 2 ) . The were determined by adding known weights of oil and gas to a methane contained less than 0.01 per cent ethane or heavier constant-temperature chamber whose volume could be varied
0.55
0' 0.50
0.45
2
4 MASS
FIGrRE
VOLLXE
4.
\7.4RIATIOS
6
8
PERCENT
OF SPECIFIC H E A T 4 T A COSSTANT SPECIFIC OF 0.035 CCBICFOOT PER POUSD WITH CHAXGE OF Mass P E R C E X T O F hlETH.4SE I N THE ?*lIXTTJRE
MASS
PERCCNT
FIGCRE 5 , BUBBLE-POIXT PRESSURE AS A FUNCTIOX OF THE h1.4SS P E R C E S T OF xfETH.4SE IN THE MIXTURE
I
INDUSTRIAL A I D ENGINEERING CHEMISTRY
986
VOL. 28, NO. 8
DISTILLATIOX O F S.4NTA FE SPRIXGS CRUDE TABLEI. ANALYTICAL Still Fraction Vapor No. Temp. O
Cumulative Recovery Mass % T'd. %
F.
Sp. Gr. of Fraction Abs. Yiscosity a t 60' F. a t 100' F. Millipoises
....
OILo
Av. Mol. Wt.
A . S. T. M. Engler Dist. Type
I
Initial
10%
O F .
Natural gasoline 3.53 Gasoline Gasoline 4 23 4.78 102 Gasoline 5.42 Gasoline 117 6.49 122 Gasoline 8.44 134 Gasoline 11.16 146 Gasoline 14.95 157 Kerosene 19.91 183 Kerosene 37.50 226 Gas oil 100.7 Gas oil 297 Residue in still; 32.83% b y wt. or ?8.98% b y vol. of the crude charged; sp. gr. a t 60' F., 0.9622; a Methane, trace; ethane, 0.014 mass per cent; propane, 0.216 per cent: isobutane, 0.286 per cent; n-pentane, 0.789 per cent. b Methane through n-pentane included in first fraction. C Absolute pressure of 30 mm. of mercury; all other fractions distilled a t 760 mm. pressure. 86 94
1
O
Distillation 50% 90%
F
O F .
LBS. P E R SQ. IN.
O
.
Av.
B. P.
F
O
68 110
F
156.7 191.0 219.4 244.5 272.0 314.6 354.5 396.1 441.6 483.0 559.8 653.5
148 .~.
184 220 264 320 368 408 446 514 600 abs. 7Tiscosity a t 210" F., 666 millipoises n-butane, 0.726 per cent; isopentane, 0.671 per c e n t ;
I
I
I
I
2
4
6
8
MASS PRESSURE
Max.
O F .
PERCENT
1
METHANE
FIGURE7 . SPECIFICVOLUMEOF TWO-PHASEMIXTURES AT 160' F.
FIGURE 6. SPECIFICGRAVITY OF MIXTURES AT 160" F. 4
4
10 .
;I
400
ma
a W a c'
0.023
L
j 0.022 U
W
4
J
0.021
9 uL-
2
0.02c
a
v1
I
2 MASS
PERCENT
FIGURE8. SPECIFIC VOLUMESEAR BUBBLE POIXTAT 160" F. AS FUNCTION OF M4ss PERCESTO F METHANE IN THE PVIIXTCRE
MASS
PERCENT
SPECIFICVOLUME O F METHANE IN FIGURE 9. PARTIAL MIXTCRES AT 160' F.
THE
INDUSTRIAL, AND ENGINEERING 2HEhIISTRI
AUGUST, 1936
VOLFMESOF MIXTURESOF METHANEAND CRUDEOIL TABLE11. SPECIFIC 4hs. Pressure Lb / s a . zn
Temp.
F. 70.0
Mass Per Cent Methane as Follous 1 414 2 367 4 323 5 106 6 062
0
(2118)
(2518)
. . . . . 0.01896 0.02210 0.02372 ..... 0.01841 0.01866 0.01893 0,02066 0.02182 . . . . . 0.01976 0.02060 ..... ..... 0.0183i 0,01860 0,01886 0.01955 0,01990 ,.... ..... . . . . . 0.01949 0 01986 0.01832 0,01855 0.01S80 0.01945 0 01978 . . . . . . . . . . 0.01942 0.01975 o:oisis 0,01860 0.01875 0.01940 0.01973
0,02604 0 02368 0 02218 0.02119 0.02050 0 02034 0.02023 0.02018
f4)a
(605)
(980)
(1796)
Bubble point 0 01860b 0 01880 0.01900 0.01962 0,01990 n 02031 300 . . . . . 0.02604 0.03620 0,05732 0 06536 0 07630 . . . . . 0.02230 0.02944 0.04536 0 05130 0 05967 400 500 0,01852 0,02019 0.02558 0.03824 0.04331 0 04965 . . . . . 0 01882 0.02306 0.03342 0.03752 0 04301 600 800 . . . . . 0 01876 0.02032 0.02789 0 03066 0 03457 1000 0.01846 0.01872 0.01900 0.02458 0 02679 0 02973
1250 1500 1750 2000 2250 2500 2750 3000 100.0
(2222)
(2604)
0.04089 0.04625 0.03565 0.04001 0.02954 0.03255 0.02587 0.02832 0.02317 0.02498 0.02150 0.02289 ..... . . . . . . . . . . 0.02046 0.02153 0.01860 0.01890 0.01914 0,01989 0.02068 ..... . . . . . . . . . . 0.01983 0.02020 0.01855 0.01884 0.01908 0.01978 0.02012 ,.... ..... . . . . . 0,01974 0.02008 0.01851 0.01879 0.01903 0.01971 0.02006
0.05304 0.04583 0,03672 0.03150 0.02746 0.02486 0.02320 0.02206 0.02126 0.02072 0.02056 0.02052
17)
1652)
(1060)
(1900)
.....
... . 0.10855 0.08332 0.06808 0.05821 0,04545 0.03834 0.03273 0.02915 0 02668 0.02497 0,02370 0.02297 0.02233 0.02191
B1ihhle point 0.01885 0,01909 0.01931 0.01993 0,02022 0.02061 300 . . . . . 0.02772 0.03888 0.06191 0.07051 0.08212 . . . . . 400 . . . . . 0.02354 0.03153 0.04876 0.05518 0.06393 0.08915 500 600 800 1000 1250 1500 1750 2000 2250 2500 2750 3000
0.01877 0.02120 0.01963 ,.... 0.01906 0.01870 0.01903
0.02730 0.02450 0.02137 0.01960 . . . . . . . . . . 0.01926 0.01866 0.01896 0,01922
130.0
(14)
(695)
(1130)
(1995)
(2321)
(2692)
B ubble point 0.01913 0.01941 0.01962 0.02025 0.02054 0.02094
300 400 500 600 800 1000 1250 1500 1750 2000 2250 2500 2750 3000
.....
0.02943 . . . . . 0.02482 0,01905 0.02216 . . . . . 0.02047 . . . . . 0.01939 0.01897 0.01935
0.04163 0.03366 0.02902 0.02594 0.02242 0.02042 ..... ..... 0.01959 0.01891 0.01927 0,01954
0.06650 0.05217 0.04355 0.03788 0.03119 0.02720 0.02420 0.02234 ..... ..... . . . . . 0.02116 0.01885 0.01920 0.01946 0.02025 ..... ..... . . . . . 0.02018 0.01879 0.01914 0,01938 0.02012 ..... ..... . . . . . 0.02007 0 01874 0.01908 0.01932 0.02003
160.0
(23)
(735)
(1190)
(2083)
400 500 600 800 1000 1250 1500 1750 2000 2250 2500 2750 3000
190.0
.....
(2415)
.....
0.02615 0,03582 0.05557 0.06292 0.07245 0.10080
0 01935 0.02311 0.03075 0.04619 0.05213 0.05982 0.08233
. . . . . 0.01131 0.02738 0.04011 0.04501 . . . . . 0.01972 0.02348 0.03284 0.03635 0.01927 0.01968 0.02124 0.02851 0.03138 ..... . . . . . 0.01994 0.02525 0,02750 0,01920 0.01959 0.01989 0.02318 0.02503 . . . . . ..... . . . . . 0,02186 0.02338 0.01913 0.01951 0.01979 0.02085 0.02224 ..... ..... . . . . . 0.02054 0.02134 0.01906 0.01944 0.01970 0.02048 0.02086 ,.... . . . . . . . . . . 0.02043 0.02079 0.01899 0.01937 0.01962 0.02038 0.02074 .
0,05152 0.06992 0,04102 0.05465 0.03504 0.04565 0.03030 0.03861 0.02723 0.03406 0.02523 0,03088 0,02381 0.02851 0.02278 0.02687 0.02204 0.02563 0,02134 0.02473 0.02123 0.02399
I
.
.
.
(58) (806) (1285) (2230) (2575) (2931) Bubble pclint 0.02013 0,02044 0.02075 0.02136 0.02168 0.02212
.. .. .. .. .. 0.02001 .. .. .. .. ..
0.03484 0.02900 0.02546 0.02309 0.02047 0.01991 0.02040
0.05050 0.04027 0.03421 0.03026 0.02560 0.02289 . . . . . . . . . . 0.01095 0.019s2 0,02029 0.02066
0.08026 0,09112 0.10541 0.06239 0.07068 0.08098 0.05150 0.05800 0.06661 0.04456 0.05000 0.05720 0.03614 0.04015 0.04542 0.03114 0.03444 0.03868 0.02735 0,03004 0.03314 0.02485 0.02716 0.02960 . . . . . . . . . . . . . . . 0.02324 0,02622 0.02726 0.01973 0.02019 0.02054 0.02215 0,02379 0.02556 . . . . . . . . . . 0.02134 0.02276 0.02430 0.01964 0.02010 0.02043 0.02124 0.02190 0.02336 . . . . . . . . . . . . . . . 0.02117 0.02160 0,02255 0.01956 0.02001 0.02033 0.02112 0.02153 0,02210 .
.
.
.
I
Figures i n parentheses refer t o bubble-point pressure, lb./sq. in. abs. cu. ft./lb.
b Specific volume,
..... .....
(2778)
(38) (772) (1242) (2162) (2499) (2859) Bubble point 0.01978 0.02007 0.02034 0.02097 0.02128 0.02167 300 0.03298 0.04742 0.07567 0.08597 0.09959 400 . . . . . 0.02754 0.03802 0.05897 0.06680 0.07671 500 0.01968 0.02423 0.03248 0,04885 0.05507 0.06321 600 . . . . . 0.02218 0.02882 0.04233 0.04750 0.05436 800 . . . . . 0.02007 0.02454 0.03449 0.03825 0.04317 1000 0.01959 0,02003 0.02206 0,02982 0.03291 0.03681 1250 . ... . . . . . 0.02033 0.02630 0.02877 0.03172 1500 0.01950 0.01993 0.02026 0.02401 0.02609 0.02842 1750 .... . . . . . . . . . . 0.02255 0.02430 0.02625 2000 0.01942 0.01984 0.02015 0.02150 0.02301 0.02469 2250 . . . . . . . . . . 0.02093 0.02205 0.02354 2500 o:oiS34 0.01976 0.02004 0.02084 0,02127 0.02270 2750 ..... ..... . . . . . 0.02078 0,02118 0.02193 3000 0.01926 0.01968 0.01995 0.02074 0,02112 0.02164 300 400 500 600 800 1000 1250 1500 1750 2000 2250 2500 2750 3000
0.07283 0.06211 0.04852 0.04078 0.03469 0.03079 0.02808 0.02615 0.02476 0,02386 0.02313 0,02260
0.07566 0.08794 0.05905 0.06819 0 : 09498 0.04919 0.05643 0,07758 0.04251 0.04867 0.06601 0.03445 0,03887 0.05159 0.02985 0,03327 0.04321 0.02624 0.02888 0.03666 0.02396 0.02605 0.03243 0.02246 0.02421 0,02948 0.02146 0.02294 0.02733 0.02062 0,02202 0.02581 0.02048 0.02138 0.02475 0,02042 0.02091 0.02393 0.02039 0.02086 0.02329
Bubble point 0.01945 0.01973 0.01996 0.02060 0.02090 0.02129 300 . . . . . 0.03118 0.04447 0,07108 0.08os1 0.09377
220.0
8 89
.....
.....
0,14107 0.10662 0.08708 0.07382 0.05772 0.04808 0.04056 0.03570 0,03229 0.02969 0.02793 0.02652 0.02552 0.02468
..
.....
0.14920 0.11244 0.09183 0.07773 0.06079 0.05051 0.04253 0.03734 0 03369 0,03087 0.02899 0.02741 0.02631 0.02537
98;
by the addition or Tvithdrawal of mercury. The corresponding equilibrium pressure at each of a series of total volumes of the system was then measured a t six temperatures between 70" and 220" F. Equilibrium was assured by a mechanical agitator within the chamber. The experimental results gave curves similar in appearance to the illustrative curves previously published for other hydrocarbon mixtures (2). The various measurements were made with sufficient precision to ensure an accuracy within the following limits: pressure, 1 pound per square inch; temperature, 0.1" F.; methane and crude oil quantities, 0.2 per cent of the mass used; volumes, 0.2 per cent, except a t the highest concentrations of methane reported where traces of asphaltic material rendered the determination of the mercury level within the equilibrium chamber difficult, Close to bubble point, occasional points showed irregularities larger than would be consistent with the above limits of accuracy; this variation was due t o the nonattainment of equilibrium a t these points. Over a thousand equilibrium points were measured to determine the pressure-volume-temperature behavior of the system summarized in Table 11. The specific heats of six mixtures of the crude oil and methane covering the same range of compositions as were used in the pressure-volumetemperature work were determined in a constantvolume calorimeter (4) throughout the same temperature range. The experimental results are shown on Figures 2 and 3, and values obtained therefrom are given in Table 111. I n each case the measured specific heats were corrected to II specific volume of 0.035 cubic foot per pound. This correction was made by graphical integration of the following expression between the specific volume a t which the specific heat was determined and a specific volume of 0.035 cubic foot per pound.
The correction was negligible a t all compositions below 5 mass per cent methane and was a maximum of 4 per cent a t the highest concentration of methane investigated. The accuracy of these measurements is considered to be 1 per cent for the higher compositions. Figure 4 shows the variation in the specific heat a t a constant volume of 0.035 cubic foot per pound with composition. The points shown were obtained from the curves of Figures 2 and 3. From the data included in Tables I1 and 111, we may calculate values of the thermodynamic properties at constant composition for this system within the temperature and pressure ranges ~ t u d i e d . ~The methods used in such calculations have been described previously ( 5 ) . Several illustrative diagrams were drawn from the tabulated data. Figure 5 shows the change in bubble-point pressure with composition for a series of temperatures. The increase in solubility a t the higher pressures and temperatures is 3 Two tables of the thermodynamlc properties of these mixtures have been piepared by the authors but apace does not permit their puhlication here Photographic copies can, however, be furnished by the authors for one dollar.
INDUSTRIAL AND ENGINEERING CHE.\fISTRY
988
T ~ B L111. E SPECIFIC HE.4TS
.4T CONSTLVT VOLUME O F AIIXTURES O F M E T H A S E A S D CRUDE O I L
Mass Per Cent Methane as Fol1oaa:1 414 2 367 4 323 5 106
7 -
're nip.
0
7
6.06%
F. 70 100 130 160 190 '70
0.495 0.476 0 515 0.498 0.535 0 519 0,555 0.540 0.575 0.562 0.595 0.583 a Specific heats reported for a specific volume of 0.035 cu. f t . per lb.
__
0 458a 0.472 0.485 0.499 0 512 0 526
0.465 0.478 0.492 0.505 0.518 0.532
0 469 0.485 0 500 0.516 0.531 0.547
0.491 0.510 0.530 0.549 0.569 0.589
marked, indicating an approach to the critical composition a t these temperatures. The change in specific gravity with equilibrium pressure for a temperature of 160" F. is depicted in Figure 6; the curve for pure methane, near the bottom, was obtained by interpolation of published compressibility data (1). Figure 7 shows the variation in specific volume TT-ith composition for the two-phase portion of the system studied. The points shown are not directly determined experimentally but were read from smooth isothermal curves drawn through the experimental points on the pressure-volume plane. The agreement of the data with a linear relation b e h e e n specific volume and composition is considered to be within the absolute accuracy of the measurements. Figure 8 is a similar diagram for the region near bubble point on a larger specific volume scale. The curvature of the isobars in the condensed region is in contrast to the straight lines in the two-phase region. The partial specific volumes, VP,under constant pressure conditions, of methane in these mixtures at 160" F. is shown in Figure 9. The partial specific volume of the dissolved methane increases somewhat as the concentration of methane in the solution is increased. The fact that the par-
VOL. 28, NO. 8
tial volume of the methane in the two-phase region is practically a constant and equal to the specific volume of methane at the same temperature and pressure indicates that there is little t'ransfer of heavy components into the gas phase a t the pressures and compositions investigated a t this temperature. S o plots of the thermodynamic properties were made since they are similar in appearance to diagrams for other mixtures published earlier (5, 6).
Acknowledgment Financial assistance for t'his work was given by the American Petroleum Institute. The Union Oil Company of California furnished the analysis of the crude oil with the exception of the molecular weight determinations. J. E. Sherborne and W.R. Mendenhall carried out several of the laboratory measurements.
Literature Cited
(3) (4)
(7) (8)
(9)
Kralnes, H. M., and Gaddy, 1 ' . L., J . .Im. Chem. SOC.,53, 395 (1931). Sage, B. H., Backus, H. S.,and Lacey, W. N., IND.ENG.CHEX., 27, 686 (1935). Sage, B. H., and Lacey, W.N., Ibid.,26, 103 (1934). Ibid.,27, 1484 (1935). Ibid., 28, 249 (1936). Am. Petroleum Inst.. Production Sage, B. H.. and Laces, V.N., Bull. 216 (1935); Oil Weekly, 80, S o . 11, 31 (1936). Sage, B. H., Lacey, W. S . , and Schaafsma, J. G., IND.ENG. C H E U . , 26, 874 (1934). Sage, B. H., Mendenhall, W.R., and Lacey, W. N., Am. Petroleum Inst., Production BuZl. 216 (1935); Oil Weekly, 80, No. 13, 30 (1936). Sage, B. H., Schaafsma, J. G., and Lacey, W. N., IND. ESG. C H E U . , 26, 1218 (1934).
RECEIVED .Ipril 13, 1936
RESISTANCE OF SOLID SURFACES TO WETTING BY WATER S THE vaterproofing of
light-weight oven or knitted fabrics, it is generally essential to preserve the air porosity of the material. The waterproofness that can be effected is therefore definitely limited by the size of the openings, because water will readily pass through if the pressure behind it is sufficient to break the surface film across the openings. FTater will penetrate, however, at a much lower pressure or even against pressure, if it can spread over the surface of the threads from one face of the cloth to the other. The waterproofing of open fabrics, therefore, presents the problem of preventing this spreading of water over the thread surfaces. The desired effect is attained by depositing on the fabric some chemical substance that has of itself this ability to resist wetting. For practical reasons, preparations intended for use in waterproofing open fabrics commonly consist of emulsions. In these preparations the active water-repellent agent is combined with other ingredients whose presence is required to ensure the desired fluidity and stability in the emulsion, to provide proper pH control, to increase the permanence of the proofing effect, and to modify the appearance and feel imparted to the finished fabric. These auxiliary constituents may impair, or they may enhance, the effectiveness of the proofing treatments. The complexity of the problem thus presented makes it desirable to study carefully the rretting characteristics of materials selected for this use. M
ROBERT N. WENZEL Mellon Institute of Industrial Research, Pittsburgh, Pa. Alaiiy substances, some n idely different chemically, are knowi and have been used as water-repelling agents. It is obvious that they must possess this property in varying degree. Yet no attempt to compare water-proofing agents on the basis of a quantitative evaluation of this essential characteristic appears t o have been macle. Moreover, few of the experimental methods that have heretofore been applied in the investigation of wetting problems are at all adaptable to the study of the wetting of different solid substances by the same liquid. The explanation probably lies in the fact that, in most cases where wetting problems are of industrial importance, the solid itself is not subject to modification or control. Attention is therefore necessarily confined to the liquid phase, its wetting power being altered either by the use of liquids of different polarity or by the introduction of surface-active solutes. A survey of possible experimental procedures led finally to the direct measurement of contact angles by the tilting plate method as the most satisfactory for comparing a wide variety of solid materials. When a suitable apparatus and proper technic had been developed, this method was found to be rapid and precise, and to afford results reproducible
