t h a t the density change p e r unit concentration is cons t a n t . One m i g h t assume the linear relationship f o r all temperatures if t h e d a t a f o r the 0.1M solution were not available. However, at higher t e m p e r a t u r e s t h e density change per u n i t concentration i s g r e a t e s t over t h e 0.0 t o 0.1M region (Table I ) , and the linear relationship between t h e density and t h e concentration of KC1 solutions applied only t o t h e 0.1 t o 1.OM region ( F i g u r e 2 ) . T h e densities of 1.27M U02SOl at t e m p e r a t u r e s t o 374" C. a r e also shown i n F i g u r e 1, together w i t h t h e d a t a of Krohn and W y m e r for 1.38M UO,SO, ( 5 ) . T h e general effect of t e m p e r a t u r e on t h e density of t h e uranyl sulfate solution i s similar t o t h a t on t h e density of t h e KCl solutions. However, t h e density of t h e U02S0, solution decreases much f a s t e r t h a n t h e density of the KC1 solutions, especially a t t e m p e r a t u r e s above 250" C. T h e divergence of t h e two sets of density d a t a f o r the U 0 2 S 0 4 solution ( F i g u r e 1) is t h e result of different solution concentrations at t h e higher temperatures. Different initial volumes of 1.27M U 0 2 S 0 4 induced different vapor volumes above the solution. Therefore, the m a s s t r a n s f e r of solvent t o t h e vapor phase w a s g r e a t e r f o r t h e lower initial volume, and the concentration of t h a t solution w a s g r e a t e r a t t h e h i g h e r temperatures. T h e densities of 0.1, 0.5, and 1.OM KC1 and of 1.27M and 1.344 molal U0,S04 a t various t e m p e r a t u r e s (Table 11) have been determined by linear interpolation of t h e density vs. concentration plots a t the various temperat u r e s . These d a t a f o r t h e KC1 solutions were interpolated f r o m t h e d a t a i n t h i s r e p o r t only. These d a t a f o r U 0 2 S 0 4 were interpolated f r o m t h e d a t a i n t h i s r e p o r t and the d a t a of K r o h n and W y m e r ( 5 ) , obtained in numerical form f r o m those a u t h o r s . T h e density change of t h e U02S0, solution f r o m 25" to 350" C. is 0.464 g r a m per ml., whereas t h e corresponding change f o r t h e 1.OM KCl solution i s only 0.320 g r a m p e r ml. T h i s difference i n the change of t h e densities m i g h t be due t o differences i n t h e concentrations or t h e molecular weights of t h e two salts. However, t h e linear relationship between t h e density and concentration of the KCl solutions indicates t h a t t h e densities of 1.27M KC1 solution a t all t e m p e r a t u r e s would be higher t h a n the densities of t h e 1.OM K C l ; b u t t h e r a t e of
Table II. Interpolated Densities of Solutions Having Constant Concentrations at Temperatures to 370" C.
Density, Grams per M1, Temp.,
c.
25 100 150 200 225 250 275 285 300 350 370
0.1 M KC1 1.003 0.971 0.933 0.882 0.858 0.823 0.788 0.773 0.743 0.618 0.525
0.5 M KC1 1.018 0.985 0.947 0.900 0.876 0.848 0.867 0.804 0.780 0.674 0.586
1.0 M
KC1 1.039 1.004 0.964 0.922 0.899 0.878 0.856 0.846 0.816 0.744 0.659
1.27 M
uozso4 1.411 1.370 1.319 1.278 1.258 1.233 1.207 1.186 1.149
1.344 rn UOZSO, 1.411 1.363 1.314 1.253 1.223 1.189 1.144 1.124 1.088
density change would not approach t h a t observed f o r U02S04. Also, normalizing t h e concentrations in t e r m s of molality a n d normality and plotting the densities a g a i n s t these t e r m s does not change the t r e n d s of, and t h e differences in, t h e densities of t h e KC1 and U 0 2 S 0 4 solutions. LITERATURE CITED
Bain, R. W., "Steam Tables 1964," Department of Scientific and Industrial Research, National Engineering Laboratory, Great Britain. Bell, J. T., Biggers, R. E., Rogers, T. G., Rom, A. M., Rev. Sci. Instr. 40,985 (1969). Copeland, C. S., Silverman, J., Benson, S. W., J . Chem. Phys. 21, 12 (1952). Ellis, A. J., Golding, R. M., Am. J . Sci. 261, 47 (1963). Krohn, N. A,, Wymer, R. G., Anal. Chem. 34, 121 (1962). Secoy, C. H., Oak Ridge National Laboratory, Chem. Div. Quart. Rept. ORNL-336, pp. 24, 26-7 (Dec. 1948). Sourirajan, S., Kennedy, G. C., U. S. Atomic Energy Commission Rept. No. UCRL-6175 (1960).
RECDIVEDf o r review April 1, 1969. Accepted October 6, 1969. Research sponsored by the U. S. Atomic Energy Commission under contract with the Union Carbide Corp.
Vapor-Liquid Equilibrium Relations of Binary Systems. The Propane-n-Alkane Systems. n-Butane and n-Pentane WEBSTER B. KAY Department of Chemical Engineering, The Ohio State University, Columbus, Ohio
I N T H E COURSE of a long-range s t u d y of t h e critical properties of hydrocarbon mixtures, P-V-2'-x d a t a have been obtained f o r a series of b i n a r y systems of the normal and branched-chain hydrocarbons. I n t h e selection of t h e systems of study, m e m b e r s of t h e homologous series of t h e paraffin hydrocarbons have been paired with a m e m b e r of t h e s a m e series, b u t of lower molecular weight. B y t h i s method, the effect of such variables a s
46
Journal of Chemical and Engineering Data, Vol. 15, No. 1, 1970
43210
molecular weight and molecular s t r u c t u r e on t h e phase behavior can be investigated a s p a r a m e t e r s f o r t h e correlation of t h e P-V-!!' d a t a . T h i s first paper summarizes the d a t a obtained f o r t h e two b i n a r y systems composed of n-butane and n-pentane, with propane a s t h e common component. T h e w o r k h a s been carried o u t by g r a d u a t e students, each b i n a r y system serving a s t h e thesis problem f o r the M.S. degree in chemical engineering.
The P-V-T-x relations of the binary systems of n-butane and n-pentane, with propane as a common component, have been determined. The experimental results cover a range from about 200 p.s.i.a. and room temperature to the highest pressure and temperature at which liquid and vapor can coexist. The data are presented in tabular form. P-1-x, density-1-x, and isobaric 1-x diagrams are given.
EXPERIMENTAL T o d e t e r m i n e t h e P-V-2"-x relations for t h e b i n a r y propane-n-alkane systems, t h e P-T border curves a n d density-temperature curves were obtained for a s e r i e s of m i x t u r e s of known composition f o r each s y s t e m , T h e relationships between a n y s e t of variables were t h e n derived by a p p r o p r i a t e cross plots of t h e curves. T h e a p p a r a t u s a n d experimental procedures were t h e
s a m e a s those employed i n earlier studies ( 5 , 6 ) . A fluid mixture, prepared by combining measured a m o u n t s of t h e p u r e a i r - f r e e components, w a s confined over m e r c u r y i n t h e sealed end of a thick-walled glass tube. T h e tube w a s heated to a constant t e m p e r a t u r e by t h e vapors of a series of p u r e organic compounds which w e r e confined i n a jacket s u r r o u n d i n g t h e tube. T h e t e m p e r a t u r e w a s m e a s u r e d t o w i t h i n 0.02" C. by a thermocouple projecting into t h e jacket. T h e t u b e w a s held i n one leg of a mercury-in-steel U-tube, t h e o t h e r leg of w h i c h w a s connected t o a source of high-pressure n i t r o g e n g a s f o r pressurizing t h e sample. T h e p r e s s u r e on t h e system w a s m e a s u r e d t o w i t h i n 0.5 p.s.i. by a precision s p r i n g gage. Both t h e thermocouple and p r e s s u r e gage w e r e calib r a t e d , t h e f o r m e r by comparison w i t h a platinum re-
TEMPERATURE .C
Figure 1 . Pressure-temperature-composition diagram for propane-n-butane system
L 0
l
l P
l
l
l
l
40 60 MOcE Ye -NE
l
l
l
80
j I20
Figure 3. Isobaric temperature-composition diagram for propane-n-butane system
I
60
80
I
I
I
I
100 120 TEMPERATURE .C
I
I
I
140
Figure 2. Temperature-density-composition diagram for propane-n-butane system
TEMF€RAWRE.C
Figure 4. Pressure-temperature-composition diagram for propane-n-pentane system Journal of Chemical and Engineering Data, Vol. 15, No. 1, 1970
47
..
60
I00
I80
140
200
MOLE Y. m t E
TEMPERATURE *C
Figure 6. Isobaric temperature-composition diagram for propane-n-pentane system
Figure 5. Temperature-density-composition diagram for propane-n-pentane system
Table I. Summary of Temperature, Pressure, and Density Relations of the Propane-n-Butane System at the Phase Boundaries ( I )
Liquid Pressure, P.S.I.A.
225.0 250.0 300.0 350.0 400.0 450.0 500.0 525.0 540.0 550.0 560.0 565.0 567.5 570.0
250.0 300.0 350.0 400.0 450.0 500.0 525.0 550.0
560.0 570.0 580.0 585,O 590.0
48
Vapor
Density, Temp., C.
g./cc.
Density, Temp..
C.
Composition. 14.68 Mole c/o Propane , . 95.8 89.9 0.4556 101.1 95.6 0.4372 110.0 105.3 0.4171 118.3 114.1 0.3950 125.8 122.1 0.3719 132.5 129.5 0.3450 138.6 136.0 0.3279 141.4 139.2 0.3140 142.9 141.1 0.3029 143.9 142.4 0.2890 144.8 143.6 0.2783 145.2 144.2 0.2720 145.4 144.5 0.2616 145.5 144.9 Composition. 30.85 Mole ... 84.ga 0.4418 94.8 0.4227 103.5 0.4029 111.5 0.3800 118.7 0.3559 125.3 0.3407 128.6 0.3238 131.6 0.3148 132.8 134.0 0.3042 0.2916 135.2 0.2820 135.9 0.2646 136.8
Liquid g./cc.
Pressure, P.S.I.A.
Journal of Chemical and Engineering Data, Vol. 15,
Density, Temp.,
C.
g./cc.
Density, Temp.,
C.
g./cc.
0.0382 0.0436 0.0480 0.0660 0.0796 0.0968 0.1191 0.1337 0.1449 0.1554 0.1710 0.1806 0.1870 0.196
250.0 300.0 350.0 400.0 450.0 500.0 525.0 550.0 570.0 590.0 600.0 605.0 610.0 614.8 max. p,
Composition. 52.11 Mole '/c Propane 71.0 82.8 81.8 0.4397 91.7 90.4 0.4213 99.4 98.1 0.4030 106.2 105.1 0.3844 112.3 111.7 0.3629 117.8 114.9 0.3504 120.3 117.9 0.3361 122.7 120.3 0.3221 124.4 122.7 0.3034 126.0 124.0 0.2899 126.6 124.6 0.2820 126.9 125.35 0.2696 127.1 126.5 0.2482
0.0402 0.0499 0.0603 0.0724 0.0863 0.1034 0.1142 0.1266 0.1380 0.1 562 0.1674 0.1726 0.1880 ...
0.0421 0.0522 0.0631 0.0758 0.0914 0.1114 0.1234 0.1385 0.1460 0.1562 0.1710 0.1804 0.1876
300.0 350.0 400.0 450.0 500.0 525.0 550.0 570.0 590.0 600.0 610.0
CompositioIn. 75.45 Mole 9;Propane 78.2 69.ga 0.4364 85.3 77.9 0.4199 91.9 0.4019 85.5 97.9 92.3 0.3832 103.2 98.4 0.3625 0.3498 105.6 101.4 104.2 108.0 0.3360 109.8 0.3240 106.4 0.3079 111.4 108.6 0.2974 112.1 109.7 0.2844 112.8 110.8
0.0484 0.0584 0.0696 0.0830 0.0984 0.1084 0.1198 0.1308 0.1441 0.1530 0.1662
7;Propane 94.1 103.4 111.0 117.9 124.2 129.9 132.5 134.8 135.7 136.6 137.5 137.8 137.9
Vapor
No. 1, 1970
Table I. (Continued)
Vapor
Liquid
~__~______
Pressure, P.S.I.A.
Temp., " C.
g./cc.
615.0 620.0 622.5
111.3 112.0 112.4
0.2766 0.2630 0.2524
Density,
Density, Temp., C. 113.1 113.3 113.36
ComDosition. 92.58 Mole 350.0
69.61' 76.6 83.1 88.8
400.0
450.0 500.0 0
Pressure, P.S.I.A.
g./cc.
0.1750 0.1868 0.1960
525,o 550.0 570.0 590.0 600.0 610.0 615.0 620.0
Propane O.Oj77 0.0694 0.0824 0.0980
72.9 79.6 85.; 91.0
0.3948 0.3735 0.3563
Vapor
Liquid -
Density,
Density, Temp., C.
g./cc.
Temp., C.
g./cc.
91.6 94.3 96.4 98.4 99.4 100.4
0.3440 0.3298 0.3165 0.3011 0.2911 0.2764 0.2658 0 .2 .514
93.5 96.0 97.8 99.6 100.4 101.2 101.6 101.9
0.1072 0.1184 0.1292 0.1424 0.1523 0.1656 0.1768 0.1822
100.9
101.4
Extrapolated value. ~__
___-__
used without f u r t h e r purification except f o r t h e removal of a i r . Deaeration w a s accomplished by a s e r i e s of operations which involved freezing w i t h liquid nitrogen a n d p u m p i n g off residual g a s over t h e solid, followed by melting of the solid sample a n d distillation at low press u r e . T h e p u r i t y of t h e components w a s checked by m e a s u r i n g t h e difference between t h e i r isothermal dew and bubble points. T h e m a x i m u m pressure difference w a s less t h a n 2.0 p.s.i. Mixtures of propane w i t h n-butane were prepared by injecting m e a s u r e d a m o u n t s of each g a s into t h e experimental t u b e , previously filled w i t h pure a i r - f r e e mercury. F o r m i x t u r e s containing n-pentane, a measured a m o u n t of the a i r - f r e e liquid compon e n t w a s t r a n s f e r r e d by molecular distillation to the experimental tube, which w a s attached to a high-vacuum line. Measured q u a n t i t i e s of pure propane g a s were t h e n injected t o make a m i x t u r e of the desired composition.
sistance thermometer which had been calibrated by t h e National B u r e a u of S t a n d a r d s , and t h e l a t t e r by comparison w i t h a calibrated dead weight gage. A previous calibration of t h e t u b e m a d e i t possible t o determine the volume of the sample by m e a s u r i n g the length of t h e t u b e which i t occupied w i t h a cathetometer r e a d i n g t o 0.02 m m . E q u i l i b r i u m between t h e liquid a n d vapor phases w a s a t t a i n e d by moving a small steel ball enclosed i n the tube, by m e a n s of a magnet, around the outside of t h e jacket. P r e s s u r e a n d volume w e r e observed a t a series of constant t e m p e r a t u r e s covering t h e r a n g e desired, MATERIALS A N D PREPARATION
OF
MIXTURES
T h e propane, n-butane, and n-pentane f r o m which the m i x t u r e s w e r e prepared were supplied w i t h a p u r i t y of 99.9 mole 7: o r b e t t e r by t h e Phillips Petroleum Co. a n d
~
Table II. Isobaric Temperature-Composition Relations of Propane-n-Butane System
Temperature,
composition^
Mole yo Propane
0 10 20 30 40 50
60 70 80 90 100
O
C.
~
Liquid
Vapor
Pressure. 300 P.S.I.A. 116.2 116.2 108.6 112.0 101.7 107.8 95.2 103.4 88.9 98.7 82.9 93.6 77.4 88.1 72.4 81.9 67.8 75.1 63.3 67.5 59.3 59.3
composition^
Mole % Propane
132.7 125.4 118.6 112.0 105.6 99.4 93.7 88.3 83.05 77.9 73.5
132.7 128.1 123.3 118.3 113.0 107.4 101.6 95.5 88.8
81.5 73.5
Liquid
Vapor
0 10 20 30 40 50 60 70 80 90 100
Pressure. 500 P.S.I.A. 146.0 146.0 139.2 141.1 132.5 135.8 125.85 130.4 119.25 124.8 113.0 119.1 107.0 113.1 101.2 106.8 95.53 100.0 90.25 92.9 85.5 85.5
0 10 20 30 40 50 60 70 80 90 100
Pressure. 550 P.S.I.A. 152.2 152.2 145,.5 146.5 138.8 140.9 132.3 135.3 125.6 129.7 119.3 124.0 113.2 118.0 107.2 111.6 101.4 104.8 95.8 97.7 90.4 90.4
Pressure. 400 P.S.I.A. 0 10 20 30 40 50 60 70 80 90 100
Temperature, C.
composition^ Mole % Propane
Temperature, O C. Liquid
Vapor
Pressure. 570 P.S.I.A. 20 30 40
142.6 137.0 131.4 125.6 119.7 113.5 106.8 100.0 92.7
140.7 134.4 128.2 121.9 115.6 109.4 103.5 97.8 92.7
50
60 70 80 90
100
Pressure. 590 P.S.I.A. 30.85 40 50 60 70 80 90 100
136.8 130.7 124.1 117.8 111.8
105.9 99.9 94.6
137.9 132.8 127.2 121.2 115.0 108.4 101.4 94.6
Pressure. 625.Oa P.S.I.A. 82.6
108.1
108.1
Maximum critical pressure for propane-n-butane system.
Journal of Chemical and Engineering Data, Vol. 15, No. 1, 1970
49
Table Ill. Vapor-Liquid Equilibrium Ratios for Propane-n-Butane System
Temp., O
Pressure, P.S.I.A. 300 350 400 450 300 350 400 450 500 550 590 300
c. 90
100
110
Temp.,
K c2 1.48 1.30 1.17 1.09 1.65 1.42 1.28 1.18 1.11 1.05 1.02 1.84
Pressure, P.S.I.A. 350 400 4 50 500 550 590
c.
K c4 0.70 0.66 0.65 0.66 0.81 0.76 0.73 0.71 0.72 0.75 0.79 0.93
110
120
K Cd 1.58 1.37 1.26 1.18
K c4 0.85 0.82 0.79 0.78 0.79 0.83
1.11
1.07
350 400 450 500 550 590
1.83 1.49 1.33 1.25 1.16
0.94 0.89 0.87 0.84 0.84 0.87
1.10
Table IV. Composition and Critical Constants of Propane-n-Butane Mixtures Critical Point Point of Maximum Pressure Point of Maximum Temperature
Temp., Temp., Mole % C1 0 14.7 30.9 52.1 75.5 82.6 92.6 100 a
(3).
Pressure, pc t P.S.I.A. 550.8~ 570.8 590.9 614.4 624.5 624.7 621.5 617.gb
T,, O
c.
152.28 145.4 137.7 126.6 113.0 108.3 101.8 96.87b
Density,
Tp, max
PCI
c.
g./cc.
0.228 0.225 0.223 0.222 0.223 0.223 0.225 0.226b
145.2 137.5 126.4 113.0 108.4 101.9
Pressure, PP,
Density,
Temp.,
TT, mar
PPI
max
mm
P.S.I.A.
g./cc.
571.0 591.7 614.8 624.5 624.7 621.5
0.251 0.241 0.235 0.222 0.233 0.220
c.
O
145.5 138.0 127.1 113.4 108.6 101.9
Pressure,
Density,
PT,
PT,
rn&X
rnax
P.S.I.A.
g./cc.
570.0 587.7 609.8 622.8 623.6 620.4
0.201 0.190 0.184 0.192 0.196 0.204
* (2). Table V. Summary of Temperature, Pressure, and Density Relations for the Propane-n-Pentane System at the Phase Boundaries (8)
Liquid
Liquid
Vapor
Vapor ~
Pressure, P.S.I.A.
O
C.
g./cc.
Density, Temp., C.
100 150 200 250 300 350 400 450 500 510 520 530
Composition. 14.70 Mole % Propane 103.4 101.0 0.520 121.2 117.0 0.497 134.8 131.5 0.474 146.5 143.4 0.451 155.8 153.2 0.430 164.4 162.1 0.406 172.0 170.8 0.378 179.0 179.2 0.341 184.7 180.8 0.332 185.8 182.5 0.320 186.6 184.2 0.302 187.2
100 150 200 250 300 350 400 450 500 550 600 610
Composition. 38.73 Mole c/c Propane 90.9 67.9 0.5396 106.8 83.7 0.518 118.5 96.7 0.499 128.1 108.4 0.4805 136.7 0.461 144.0 119.1 151.2 128.3 0.441 156.9 136.8 0.421 144.8 0.398 162.0 152.8 0.371 166.5 161.2 0.325 168.4 167.7 163.3 0.305
100
150 200 250 50
Density, Temp.,
Composition. 61.62 Mole 96 Propane 80.1 48.2 0.539 93.5 62.3 0.518 103.2 74.5 0.499 111.6
g./cc.
...
... ... ...
0.075 0.093 0.117 0.147 0.157 0.170 0.186
... ...
... ...
... 0.082 0.097 0.115 0.143 0.178 0.158
... ... ...
Journal of Chemical and Engineering Data, Vol. 15, N o . 1, 1970
Pressure, P.S.I.A.
Density, Temp.,
O
C.
g./cc.
Temp., ' C
300 350 400 450 500 550 600 650
Composition. 61.62 Mole 85.3 0.480 95.1 0.462 103.5 0.444 111.5 0.424 118.8 0.404 126.2 0.380 132.9 0.352 140.8 0.299
150 200 250 300 350 400 450 500 550 600 650
Composition. 78.62 Mole c/c Propane 71.2 52.2 0.491 81.6 63.5 0.474 90.2 73.2 0.458 97.5 81.6 0.442 104.0 89.3 0.426 109.8 96.5 0.408 115.2 103.2 0.389 119.9 109.8 0.367 124.0 115.9 0.341 127.1 122.8 0.287 128.5
250 300 350 400 450 500 550 600 650
Composition. 87.78 Mole yo Propane 56.9 0.467 79.7 66.3 0.449 86.3 74.5 0.433 92.2 82.2 0.415 97.0 89.2 0.398 102.1 95.4 0.379 106.5 101.3 0.357 110.5 107.1 0.328 113.9 113.4 0.255 115.5
c/o
Density,
Propane 118.2 124.6
g./cc.
, . .
... ...
134.8 139.4 143.2 146.2 146.8
0.085 0.100 0.119 0.145 0.155
...
... ... 0.056 0.067 0.079 0.094 0.112 0.135 0.173 ...
... ...
... 0.078 0.092 0.110 -
0.135 0.200
Table VI. Isobaric Temperature-Composition Relations of Propane-n-Pentane System
Composition, Mole % Propane
0 10 20 30 40 50 60 70 80 90 100
Liquid,
Vapor,
c.
a
c.
Composition, Mole yc Propane
Pressure. 300 P.S.I.A. 165.2 165.2 150.4 157.94 135.7 150.6 121.1 142.8 134.7 106.6 126.7 95.4 118.1 86.6 108.3 78.9 71.9 96.7 81.7 65.3 58.8 58.8 -
0 10 20 30 40
50 60 70 80 90 100
Liquid,
Vapor,
c.
c.
Pressure. 400 P.S.I.A. 114.9 140.9 105.0 131.1 96.1 120.6 88.1 108.1 80.4 92.9 73.0 73.0
Pressure. 500 P.S.I.A. 194.6 194.6 185.0 188.7 171.1 179.9 157.1 170.6 143.2 160.7 131.3 150.8 120.1 140.9 110.6 130.4 101.9 117.9 93.3 103.2 85.00 85.0 100 3.2 10 20 30 40 50 60 70 80 90
.essure. 400 P. I.A. 183.3 183.3 175.8 168.9 167.7 154.4 158.9 140.2 150.0 126.4
Composition, Mole 70 Propane
Liquid, O
Vapor,
c.
c.
Pressure. 600 P.S.I.A. 33.7 171.1 171.1 38.73 161.4 168.4 40 159.4 167.2 50 146.1 158.0 60 134.5 148.2 70 124.3 137.2 80 114.6 125.0 90 105.0 110.6 100 95.2 95.2 Pressure. 650 P.S.I.A. 55 151.7 151.7 60 142.7 148.3 70 131.7 138.6 80 121.6 126.9 87.76 113.3 115.6 88.6 113.3 113.3
Table VII. Vapor-Liquid Equilibrium Ratios for Propane-n-Pentane System
Temp., Pressure, C. P.S.I.A.
K C ~
Kcj
Temp., Pressure, a C. P.S.I.A.
K C ~
K CB 0.506 0.472 0.490 0.627 0.609 0.541 0.544 0.634
90
300 400 500
1.52 1.18 1.036
0.342 0.371 0.425
110
300 400 500 600
1.82 1.44 1.21 1.067
100
300 400 500 600
1.69 1.31 1.12 1.02
0.416 0.417 0.458 0.626
120
300 400 500 600
1.88 1.55 1.30 1.125
Temp., Pressure, C. P.S.I.A. 120 150
180
650 300 400 500 600 650 400 500
K
c3
1.044 2.03 1.74 1.45 1.24 1.05 1.96 1.46
K cj 0.808 0.882 0.779 0.757 0.791 0.933 0.976 0.928
Table VIII. Critical Constants of Propane-n-Pentane Mixtures
Critical Point Mole 76 Propane 0 14.7 38.7 61.6 78.6 87.8 100 a
(3).
Point of Maximum Pressure
T P miix Temp., C. O
196.G 187.0 166.8 144.7 126.1 114.3 96.Wb
Pressure, P.S.I.A. 489.P 538.1 614.0 657.7 662.0 651.8 617.gb
Density, g./cc. 0.232~ 0.241 0.244 0.240 0.235 0.231 0.226h
P P
rnax
Point of Maximum Temperature
c.
pressure, P.S.I.A.
Density,
Temp., ' C. TT m a x
PT Illax
Density,
g./cc.
P.S.I.A.
g./cc.
186.3 165.4 144.3 126.5 115.0
539.1 616.3 658.0 662.0 652.0
0.326 0.278 0.259 0.242 0.246
187.4 168.5 147.3 128.6 115.7
533.7 595.0 636.0 650.0 643.0
0.190 0.190 0.180 0.170 0.180
temp.,
* (2).
T h e e s t i m a t e d e r r o r in t h e composition of t h e m i x t u r e p r e p a r e d in t h i s m a n n e r w a s about 0 . 5 7 ~ . EQUILIBRIUM DATA
The pressure-temperature and density-temperature d i a g r a m s f o r m i x t u r e s of c o n s t a n t composition, a n d t h e isobaric temperature-composition d i a g r a m s f o r propanen - b u t a n e a n d propane-n-pentane s y s t e m s a r e shown in F i g u r e s 1 t h r o u g h 6. F r o m l a r g e plots of these figures, Tables I t h r o u g h VI11 w e r e constructed, g i v i n g smoothed values of t h e t e m p e r a t u r e s a n d densities at t h e bubble and dew points f o r m i x t u r e s of c o n s t a n t composition at r e g u l a r i n t e r v a l s of p r e s s u r e , t h e bubble a n d dew points
a t r e g u l a r i n t e r v a l s of t h e composition a t a s e r i e s of c o n s t a n t pressures, t h e vapor-liquid equilibrium r a t i o K = y/x,a s a f u n c t i o n of p r e s s u r e a t a series of selected t e m p e r a t u r e s , a n d t h e p r e s s u r e , t e m p e r a t u r e , a n d density a t t h e critical point, maximum p r e s s u r e point, a n d maxim u m t e m p e r a t u r e points on t h e P-T b o r d e r curves f o r each of t h e m i x t u r e s of t h e two b i n a r y s y s t e m s t h a t w e r e studied. T h e tables f o r each system a r e grouped t o g e t h e r a n d a p p r o p r i a t e l y marked. T h e critical point w a s d e t e r m i n e d visually b y t h e disappearance-of-themeniscus method, w h e r e a s t h e p r e s s u r e a n d t e m p e r a t u r e a t the maximum pressure and maximum temperature points were obtained graphically f r o m l a r g e plots of t h e Journal of Chemical and Engineering Data, Vol. 15, No. 1, 1970
51
P-T b o r d e r curves i n t h e critical r e g i o n of t h e m i x t u r e . T h e accuracy of t h e tabulated d a t a i s e s t i m a t e d as follows : t e m p e r a t u r e , * 0.5" C. ; pressure, 2.0 p.s.i. ;
*
density, *0.001 g r a m p e r cc. f o r t h e liquid a n d *0.0001 g r a m p e r cc. f o r t h e vapor. However, i n t h e critical region, t h e u n c e r t a i n t y i n t h e values reported m a y be somewhat g r e a t e r , because of t h e difficulty i n a s s e s s i n g t h e accuracy of m e a s u r e m e n t s i n t h i s region.
ACKNOWLEDGMENT G r a t e f u l acknowledgment i s m a d e to t h e Union Carbide Corp., Linde Division, a n d t o t h e A m e r i c a n Cyanamid Co. f o r financial a i d i n t h e f o r m of a fellows h i p to J. R. B a r b e r , a n d to t h e Phillips P e t r o l e u m Co. f o r samples of p u r e hydrocarbons. LITERATURE CITED
COMPARISON OF RESULTS WITH LITERATURE DATA T h e propane-n-butane system w a s studied b y Nysew a n d e r et al. ( 7 ) a n d t h e propane-n-pentane s y s t e m b y S a g e a n d Lacey ( 9 ) . A n a p p a r a t u s s i m i l a r t o t h a t employed in t h i s s t u d y w a s used. In T a b l e I X (deposited w i t h A S I S ) a comparison is m a d e between the values of t h e t e m p e r a t u r e a n d p r e s s u r e at t h e critical point, maxim u m p r e s s u r e point, a n d m a x i m u m t e m p e r a t u r e point reported f o r t h e s e s y s t e m s a n d t h o s e f o u n d i n t h i s s t u d y . T h e a g r e e m e n t i s moderately good f o r both systems, b u t noticeably b e t t e r f o r t h e propane-n-pentane system. Table X (deposited w i t h A S I S ) compares bubble a n d dew point d a t a f o r t h e propane-n-butane system. The d e w point p r e s s u r e s of m i x t u r e s of low p r o p a n e content a g r e e moderately well w i t h those f o u n d i n t h i s s t u d y ; f o r m i x t u r e s of h i g h p r o p a n e content, t h e a g r e e m e n t is less s a t i s f a c t o r y . T h e bubble point p r e s s u r e s show f a i r l y l a r g e deviations. T h i s is d u e t o t h e g r e a t e r s e n s i t i v i t y of t h e bubble point p r e s s u r e , compared to t h e d e w point pressure, to small t r a c e s of noncondensable gas in t h e sample.
Barber, J. R., M.S. thesis, Ohio State University, Columbus, Ohio, 1964. Barber, J. R., Ph.D. thesis, Ohio State University, Columbus, Ohio, 1968. Hoffman, R. L., M.S. thesis, Ohio State University, Columbus, Ohio, 1962. Kay, W. B., I n d . Eng. Chem. 32, 358 (1940). Kay, W. B., J . Am. Chem. SOC.69, 1273 (1947). Kay, W. B., Rambosek, G. M., I n d . Eng. Chem. 45, 221 (19531. Nysewander, C. N., Sage, B. H., Lacey, W. N., Ibid., 32, 118 (1940). Oxley, J. A., M.S. thesis, Ohio State University, Columbus, Ohio, 1963. Sage, B. H., Lacey, W. N., I n d . Eng. Chem. 32, 992 (1940). ~
~~~
RECEIVEDfor review April 10, 1969. Accepted October 3, 1969. For Tables IX and X, order N A P S Document NAPS00651 from ASIS National Auxiliary Publications Service, c/o CCM Information Sciences, Inc., 22 West 34th St., New York, N. Y . 10001. Remit $1.00 for microfiche or $3.00 for photocopies.
l o w Temperature Heat Capacities of 15 Inorganic Compounds D.
R. STULL, D. L. HILDENBRAND,'
Thermal Research Laboratory, The
F. L. OETTING,2 and G . C. SlNKE
Dow
Chemical Co., Midland,
Mich. 48640
Smoothed low temperature heat capacities and derived thermodynamic functions for KOH, K,CO,, K,SiO,, K,S,O,, KBH,, LiCI, LiBO,, Li,SiO,, MgS, Mg(CO,H),, P,O,,,, BPO,, SnSO,, Na,SiF,, and AICI, * 6H,O are presented at even temperatures. Comparisons with literature data indicate the entropies at 298.15O K. are accurate to at least 1%. Such values are useful in thermodynamic calculations, as evidenced by comparison with estimates based on ion contributions.
D U R I N G T H E P A S T D E C A D E a n d a half, t h e pio n e e r a u t o m a t i c a d i a b a t i c low-temperature calorimeter described by Stull ( 1 3 ) w a s used f o r t h e m e a s u r e m e n t of t h e h e a t capacity of a n u m b e r of i n o r g a n i c solids. T h e precision of m e a s u r e m e n t a t t a i n e d w i t h t h i s calor i m e t e r w a s s o m e w h a t less t h a n could be achieved w i t h manually operated a p p a r a t u s . Samples used w e r e t h e best available w i t h i n t h e t i m e l i m i t a t i o n s of a n indust r i a l l a b o r a t o r y ; in some cases t h i s m e a n t relatively low p u r i t y a n d i n o t h e r s incomplete characterization. Heat capacity m e a s u r e m e n t s a r e n o t highly sensitive t o impurities, however, a n d t h e smoothed h e a t capacity 1 Present address : Douglas Advanced Research Laboratories, Huntington Beach, Calif. 92647 2Present address: The Dow Chemical Co., Rocky Flats Division, Golden, Colo. 80401
52
Journal of Chemical and Engineering Data, Vol. 15, No. 1,
l9YO
d a t a led to third-law entropies of good accuracy as shown by some comparisons w i t h d a t a f r o m o t h e r laboratories. Therefore, although t h e m e a s u r e m e n t s m a y n o t w a r r a n t a detailed account of individual d a t a points, smoothed tables of thermodynamic f u n c t i o n s at even t e m p e r a t u r e s should prove useful i n thermodynamic calculations.
MATERIALS R e a g e n t g r a d e potassium hydroxide w a s d r i e d u n d e r vacuum at 425" C. Analysis b y acid t i t r a t i o n indicated 97.8% K O H a n d 2.2% K2C0,. R e a g e n t g r a d e potassium c a r b o n a t e w a s d r i e d at 300" C. T h e m a n u f a c t u r e r ' s analysis i n d i c a t i n g 99.97" p u r i t y w a s accepted. A sample of potassium metasilicate w a s prepared f r o m
