sobaric
t Capacities at
c~s-Z-BUTENE,ISOPROPY LBENZENE, AND n-DECANE W. G. SCRLINGER AND B. H. SAGE Calgomia Institute of Technology, Pasadena 4, CalW.
A
VAIEABLE experimental inforniatioit concerning t h r heat capacity of cis-%butene in the liquid phase is limited to how temperatures. Todd and P a r k (26) investigated the heat capacity of the liquid from -210" to 20" F. utilizing an aneroid calorimeter. Scott and coworkers ( 2 0 ) also determined the heat capacity of this compound a t temperatures up to 80" F. They calculated the heat capacity of the gas in the ideal state from spectroscopic data over a substantial range of temperatures. &ull (24) established values for the heat capacity of the gas a t (,emperatures from -10" to 2240" F. from spectroscopic data. Spencer ($2) correlated the available spectroscopic data and prrsented an empirical equation for the heat capacity of cis-2-but,ene at infinite attenuation. Kurbatov ( 7 ) investigated the heat capacity of liquid isopropylbenzene and reported an equation for the molar heat capacity from 60' to 290' F. KolosovslciI and Udovenko (6) determined the isobaric heat capacity a t a single temprrature along with the isothermal entropy-pressure coefficient. Decane has been investigated in somewhat greater detail than isopropylbenzene. Huffman, Parks, and coworkers (5, I f ) determined the heat capacities of the solid and the liquid phases at temperatures up to 75' F. with good accuracy. Osborne a d Ginninys (IO)reported values of the heat capacity a t bubble point. Schultz (19) proposed a generalization of the heat capacity of hydrocarbon gases a t low pressures which was extended recently by Pitzer (12). The thermodynamic properties of the lighter hydrocarbons were critically reviewed by Rossini (f 5 ) . MATERI4LS
and was found to have a refractive index relative to the o-lines of sodium of 1.4909 at a temperature of 68" F., as compared to a value of 1.49125 reported by Forziati and coworkers (4)and a value of 1.4911 by Troyan (26). The specific gravity at 77" F. was found to be 0.85745 as compared to a reported value of 0.85748 by Forziati and coworkers (4). These data indicate that the fluid employed was nearly pure isopropylbenxene. On the basis of a linear change in the index of refraction with composition it was estimated that the probable impurities were not more than 0.002 mole fraction. The n-decane was obtained from Research Project 44 of the American Petroleum Institute and was reported to be substantially pure. The sample as received was subjected to a single fractionation a t reduced pressures to eliminate the air dissolved during shipment. The fractionated sample had a refractive index of 1.4119 for the d i n e s of sodium a t 68" F. as compared with a value of 1.41203 reported by Shepherd ( 2 1 ) and a value of 1.41189 reported by Forziati (4). On the basis of the measured value of the refractive index it is probable that the impurities were not greater in amount than in the sample used by Forziati (4),which waa reported as 0.003 mole fraction. The purity of each of the samples investigated was sufficient that no uncertainty in the heat capacities resulted from their use. The heat capacity of most hydrocarbons a t a distance from the critical state lies between 0.4 and 0.6 B.t.u. per pound and the majority of the impurities encountered are usually closrly allied compounds which do not differ from the primary substance by more than 10% in heat capacity. On the basis of ideal solutions the presence of 0.002 mole fraction of impurity will result in only 0.02% error in the heat capacity, which is less than one fourth of the standard deviation of the heat capacity measurements and about 2% of the estimated total uncertainty of measurement,
The cis-%butene was procured from the Phillips Petroleum Go. with the statement that the material contained less than 0.002 mole fraction of material other than cis-2-butene. This aamule exhibited lesi than 0.2 pound per square inch change in vapor pressure at 190' F. as a result of a change in the weight fraction vaporized from 0 9.45 i 0.2 to 0.9. It was ID miployed without 0 purification other 0.40 than the removal of a i r b y p r o > longed evacuation t at the tempera2 0.35 4 LJ ture of liquid nitrogen The isopropylbenzene was obTEMPERATURE I ained from the Figure 1. Experimental Results for &-%-Butene kame company 2454 7
O F
EXPERIMENTAL MEASUREMENTS
The measurcments were made in the heterogeneous region with a calorimeter which was described earlier ( 2 , 3, 16, 28). KO changes were made in the techniques which xcre used for the study of propene, neohexane, cyclohexane, and iwoctane ( 2 ) . The energy required t o change the temperature of the
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INDUSTRIAL AND ENGINEERING CHEMISTRY
October 1952
calorimeter and contents was determined for each of two quantities of the compound under investigation. Figure 1 presents experimental results for cis-&butene. Experimental measurements for isopropylbenzene and n-decane were comparable in density and in agreement with a smooth curve. The standard deviation of the data shown in Figure 1 expressed as a fraction of the difference between the two curves is 0.028. Corresponding standard deviations for isopropylbenzene and n-decane are 0.012 and 0.0090, respectively. The calculated standard errors, thestandard deviations of the derived curves from curves established by an infinite number of experimental points, expressed as fractions, are 0.005, 0.002, and 0.002 for cis-Zbutene, isopropylbenzene, and n-decane, respectively. The isobaric heat capacities at bubble point were computed from the two sets of calorimetric measurements and the coefficient, c, by means of the following expression:
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in some detail and for present purposes recent measurements extending over the temperatures of interest were employed (14, 17). The volumetric correction of the thermodynamic data was small in this case also. Uncertainties in the factor, c, for isopropylbenzene and n-decane contributed less than 0.1% to the uncertainty in the reported values of the isobaric heat capacities.
8
0.00
>
5
2j 0.55 r;
The method for evaluating the volumetric correction factor, c, has been discussed elsewhere (9,8). Values of this factor for cis-2-butene, isopropylbenzene, and n-decane are shown as functions of temperature in Figure 2. These curves show that the volumetric corrections are relatively small except in the case of cis-2-butene. The requisite correction (18) of the isochoric data for cis-2-butene was based upon volumetric data for 1butene ( 9 ) since there did not appear to be eomparable data for
u
bo
E
0.10
2
B
5
0.05
U
0.00
I
I
ioo
I20
I I40 TEMPERATURE
I
I
I60
180
I
OF
Figure 2. Volumetric Corrections to Calorimetric Measurements
cis-2-butene. The experimental information for 1-butene was applied at the same reduced states and did not introduce significant uncertainty in the results. The available experimental information for isopropylbenzene was not sufficient t o permit the direct evaluation of corrections to the calorimetric data obtained in the heterogeneous region. However, since the vapor pressure was low and the material was far removed from its critical temperature, the corrections were small. Thus it was possible to utilize the law of corresponding states to determine the volumetric corrections. The critical temperature and pressure were estimated from the work of Prudhomme (13) and Altschul (1) which agreed with the critically chosen values reported by Rossini (16). The volumetric behavior of the liquid phase of n-decane has been investigated
Y
9 0.50 d
m
4
SCOTT, FERGUSON, BRICKWEDOE
AND
8
The detailed experimental measurements of the heat capacities of the calorimeter and contents are available (38). From these data and the corrections presented in Figure 2, the isobaric heat capacities were established. It is estimated that these values may involve uncertainties of as much as 1.5% for the cis-2butene and 1% for the other two hydrocarbons. The larger probable error for the cis-2-butene resulted from uncertainties in establishing the volumetric correction factors recorded in Figure 2. Values of C, for cis-%butene for low temperatures, obtained by applying a thermodynamic conversion to the values of heat capacity at bubble point reported by Scott and coworkers (BO), have been recorded with the results of the present investigation in Table I. Figure 3 portrays the isobaric heat capacity of cis-%butene at bubble point as a function of temperature. Reasonable agree ment appears to have been obtained with the measurements of Todd and Parks (96)and of Scott and coworkers (BO). Similar information for isopropylbenzene and for n-decane is presented in Figure 4. The single measurement of KolosovskiI and Udovenko (6) is included for comparison in the case of isopropylbenzene. The deviation of Kurbatov’s line from the results of the present investigation is less than the combined uncertainties in the experimental measurements. The data for n-decane of Huffman, Parks, and coworkers (6,11) at relatively low temperatures and those of Osborne and Ginnings (10) are shown. There was satisfactory agreement between the Huffman results and those of the present investigation. The values from these two investigations are approximately 1yo lower than those reported by Osborne and Ginnings. Values of the isobaric heat capacity a t bubble point for isopropylbenzene and n-decane are recorded in Table 11. NOMENCLATURE
c
C,
m
S_
T
= volumetric correction factor = isobaric heat capacity, B.t.u. per (pound) ( R.) =
weight of material in calorimeter, pounds
= heat associated with infinitesiFal change in state, B.t.u. = thermodynamic temperature, R.
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INDUSTRIAL AND ENGINEERING CHEMISTRY
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Vol. 44, No. 10
(1) Altschul, Xi., Z . physik. Chem., 11, 590
(1893). (2) l u e r b a c h , C. E., Sage, B. H., and Lacey, W. S . ,IND. ENG.CHEV.,42, 110 (1950).
(1946). (5) Huffman, H. hI., Parks, G. S., and Rarmore, &I., J . Am. Chem. Soc., 53, 3876 (1931). HEdT CAPACITY OF CiS-2-BUTENE AT BUBBLE TABLE I. ISOBARIC (6) Kolosovskii, N., and Udovenko, 1‘.V., J . Gen. Chem. (G.S.S.R.), POINT 4 , 1027 (1934). ‘Pb, CP*’ (7) Kurbatov, V. Ya., Ibid., 17, 1999 (1947). B .t .u ./ Temp., B.t.u./ Temp., (8) Lacey, IT.N., and Sage, B. H., “Thermodynamics of One(Lb.) (” R.) F. (Lb.) (” R.) F. Component Systems,” Pasadena, Calif., California Institute -220 of Technology, 1947. -210 (9) Olds, R. I$., Sage, B. H., and Lacey, W.N., IND.ENG.CHEM., -200 38. 301 11946). - 190 -180 (10) Osborne, 9. S.;and Ginnings, D. C., J . Research Nail. Bur. - 170 Standards, 39, 453 (1947). -160 (11) Parks, G. S., Huffman, H. &I., and Thomas, S. B., J . Am. -150 - 140 Chem. Soc., 52, 1032 (1930). - 130 (12) Pitzer, K. S., IND. ENG.CHEM.,36, 829 (1944). - 120 (13) Prudhomme, SI.,J . Chem. Phys., 94, 2704 (1920). -110 - 100 (14) Reamer, H . H., Olds, R. H., Sage, B. H . , and Lacey, W. N., -90 IND. EXG. CHEM.,32, 743 (1940). - 80 (15) Rossini, F. D., “Selected Yalues of Properties of Hydrocar- 70 - 60 bons,” Washington, D. C., National Bureau of Standards, - 50 1947. - 40 (16) Sage, B. H . , Evans, H. D., and Lacey, W. N., IND. ENG.CHEM., - 30 -20 31, 763 (1939). - 10 0.4969 (17) Sage, B. H., Lavender, H . W., and Lacey, W.N., Ibid., 32, 743 11940). a Values from SOo t o 200” I‘. are the authors’ experimental work. Values from -220° to 70’ F. were obtained b y applying a thermodynamic conver(18) Schlinger, \Ir. G., and Sage, B. H., Ibid., 41, 1779 (1949). sion t o the saturation values reported b y Scott a n d coworkers (20). (19) Schults, J. W.,Ibid., 22, 785 (1930). (20) Scott, R. B., Ferguson, W. J., and Brickwedde, F. G., J . ReHEATCAPACITIES OF ISOPROPYLBENZEXE search Natl. Bur. Standards, 33, 1 (1944). TABLE 11. ISOBARIC AND %-DECANE AT BUBBLEP O I N T (21) Shepherd, A. F., Henne, A. L., and Midgley, T . , Jr., J . Am. Cham. Soc., 53, 1948 (1931). Temp., IsopropylF. benzene n-Decane (22) Spencer, H . M., Ibid., 67, 1859 (1945). (23) Stewart, R. M., Jr., Haygood, J. LI., Pings, C. J., Jr., Schlinger, 0.4161a W.G., and Sage, B. H., American Documentation Institute, 0.4215 0.4267 Washington, D. C., Document No. 3507 (1952). 0.4318 (24) Stull, D. R., I N D .ENG.CHEM.,35, 1303 (1943). 0.4371 (25) Todd, S. S., and Parks, G. S., J . Am. Chem. Soc., 58, 134 (1936). 0,4425 0,4482 (26) Troyan, J. E., Ibid., 64, 3056 (1942). 0,4541 0.4600 0,4660 0.4720 0.4778 0.4837 5
Isobaric heat capacity a t bubble point, B.t.u. per (pound)(’ R.).
RECEIVED for review January 24, 1952. ACCEPTED April 28, 1952. For material supplementary t o this article order Document 3507 from American Documentation Institute, 1719 N Street, N.W., Washington 6, D. C., remitting $1.00 for microfilm (images 1 inch high on standard 35 mm. motion picture film) o r $1.00 f o r photocopies (6 X 8 inches) readable without optical aid.
Subscripts b = bubble point 1 . 2 = conditions with different quantities of samples in calorimeter ACKNOWLEDGMENT
R. &I. Stewart, Jr., J. M. Haygood, and C. J. Pings, Jr., were recipients of the California Research Corp. fellowships. Each one contributed materially to the experimental work reported.
Correction We are indebted to Charles H. Hughes for the following correction. Reference (2E) in the article “Oil Gas Rlanufacture” [IND. ENG.Cmiv., 44, 948 (1952)] should read: (2E) Brassert, H. h.,& Co., New York, N. Y . , coke plant containing four Knowles-type ovens, modified by Hughes By-product Coke Oven Corp., New York, N. Y .
