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AND WADDINGTON Vol. 78 PENNINGTON, SCOTT,FINKE,MCCULLOUGH, MESSERLY, HOSSENLOPP
Thermochemical Calculations.-The vapor pressure measurements of Smith, Line and Bell3 on rhenium heptoxide and perrhenic acid make possible the calculation of the following entropy changes at 298.16"K. R e ~ O d c )= RezOdg) AS' = 55.5 f 0.2 cal. deg.-l mole-'
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2HRe04(c) = Re207(c) HnO(gj AS" = 22.0 f 0.1 cal. deg.-l mole-'
(1) (2)
These data combined with the above value for the entropy of rhenium heptoxide (49.54 cal. deg.-' mole-') and the entropy of HnO(g) (45.13 cal. deg.-' give S&,, (Re20,ig),ideal gas at 1 a t m . ) = 105.0 f 0.3 cal. deg.-l mole-'
S,",,,,, (HReOi(c)) = 36.4 i 0.2 cal. deg.-l mole-'
Two separate determinations of the heat of formation of rhenium heptoxide have been made; Roth and Becker" obtained -297.5 + 2.0 kcal. (10) K. K. Kelley, Bureau of Xines, Bulletin 477, 1950. (11) W. A . R o t h a n d G. Becker, Z . p k y s i k . Chem., A169, 27 (1932). D a t a have been recalculated and summarized in Bureau of Standards Circular 600 "Selected Values of Chemical Thermodynamic Properties," 1962. -
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mole-', and Boyd,12 et al., obtained -295.9 + 2.0 kcal. mole-'. The average of the two values, -296.7 =t 2.0 kcal. mole-', combined with the entropy of formation, - 139.78 cal. deg.-' mole-1s13 gives -255.0 i= 2.0 kcal. mole-' for the free energy of formation of rhenium heptoxide. The free energy of formation of crystalline perrhenic acid, -157.0 =t1.0 kcal. mole-', may be obtained from the free energies of formation of HnO(g) (-34.64 kcal. mole-')14 and Re'OT(c) (-255.0 kcal. mole-') combined with the standard free energy change of reaction (21, 4.5 kcal. mole-', computed from the vapor pressure equation of Smith,3 et al. Acknowledgments.-It is a pleasure to acknowledge the considerable assistance of Dr. G. E. Myers who assisted with the benzoic acid and rhenium heptoxide measurements, of Dr. E. Eichler and Mr. Henry Dearman who assisted with the measurements and calculations. (12) G. E. Boyd, J. W. Cohhle and Wm. T . Smith, Jr., THISJ O U R 76, 5783 (1953). (13) Sf;, = 8.89 cal. deg.-l mole-', Wm. T. Smith, Jr., G . D. Oliver a n d J. W.Cobble, ibid., 76, 6785 (195.73, and .S& = 49.01 cal. deg.-] mole-], K . K. Kelley, ref.10. (14) F. D . Rossini, e l d., Bureau of Standards Circular 600, "Selected Values of Chemical Thermodynamic Properties," 1952. KAL,
OAKR I ~ G ETENSESSEE ,
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THERMODVXAMICS LABORATORY, P E T R O L E U M EXPERIMENT STATION, BUREAUOF MISES]
The Chemical Thermodynamic Properties and Rotational Tautomerism of 1-Fropanethioll BY R. E. PENNINGTON, D. IT.SCOTT,H. L. FINKE, J. P. MCCULLOUGH, J. F. XESSERLY, I. HOSSENLOPP AND Gnu WADDINGTON RECEIVEDJ A N U A R Y 21, 1956 Experimental and computational studies were made of the thermodynamic properties of 1-propanethiol in the temperature range 0 to 1000°K. The experimental studies provided the follorving information: values of heat capacity for the solid, the liquid [Csntd = 45.862 - 0.15070 T f 5.0219 X lo-+' T 2 - 4.167 X 10-7 T 3 ,cal. deg.-l mole-' (180 to 320°K.)],and the P,cal. deg.-l mole-' (331 t o 600°K.j] ; the heat of transition vapor [ C i = 3.733 7.123 X 1,0-2 T - 2.721 X 1949.1 cal. mole-'] a t 142.10"K.; the heat of fusion [1309 cal. mole-'! a t the triple point [160.00f O.O5"K.]; the entropy in the saturated liquid state at 298.16'K. [57.96 cal. deg.-' rnole-'j : the heat of vaporization [ A H v = 9855 - 2.55lT 1.668 x 10-2Tz cal. mole-1 (303 to 341°K.)] ; the second virial coeficient, B , in the equation of state, PI' = RT(1 B,'V!, [ B = -32 - 91.7 esp (800/T), cc. mole-' (303 to 500°K.)]; the standard heat of formation of liquid 1-propanethiolfroni graphite, hydrogen and rhombic sulfur at 298.16'K. [-23.69 i 0.16 kcal. mole-'] ; and the vapor pressure [log,, p ( m m . ) = 6.92846 - 1183.307/(t 224.624), (24 t o 1 0 2 O ) ] . Tables of the thermodynamic properties in the solid and liquid states (10 to 320°K.) were computed. Experimentally determined properties of the vapor (SOand C,O) were used with spectroscopic and molecular structure information t o evaluate barriers t o internal rotation and the energy difference between the rotational tautomers of 1-propanethiol (the trans skeletal configuration is more stable by about 400 cal. mole-'). Tables of the chemical thermodynamic properties in the ideal gaseous state a t selected temperatures from 0 to 1000'K. were computed.
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As part of American Petroleum Institute Research Project 48A, this Laboratory is conducting investigations of the chemical thermodynamic properties of organic sulfur compounds that occur in petroleum or petroleum products. Comprehensive studies are made of "key" members of various homologous series of sulfur compounds. The data obtained in these detailed studies will form the basis for calculating, by approxiniate statistical iiiechanical methods,' thermodynamic information for many other members of each series studied. The (1) This investigation was p a r t of American Petroleum Institute Research Project 48.4 o n "The Production, Isolation a n d Purification of Sulfur Compounds and Measurement of Their Properties," which the Bureau of Mines conducts a t Bartlesville, Okla., a n d Laramie, %.yo. ( 2 ) E . & , (a) I; S. Pitzer and J. E. Kilpatrick, Cheni. Revs.. 39, 438 (1946); (h) J . l
