-
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
1945
the point of crossing the 46' line) is, however, extremely dight. The peculiarities of this system ~ 1 due to, or illustrated by, the fact that the right hand solubility line, as indicated on the right-hand dashed line of the x y plot falls to the left of the 45' diagond.
TABLEVII. VAPOBCOMPOBITXON DATAFOR MEETHYL KETONEwATEB '=TEW AT INDlCAmD p ~ m -IlllllrmAL DATA) 760 Mm. H g 5
'g.8 88.4 86.4 84.2 80.0 78.1 y.9
-
I'U.
Y
0
--
600 Mm. H g u .ic'L 66.8 68.6
79.e 100 I& 80.8 76.6 90.6 80.8 76.9 74.8 86.0 76.8 74.8 74.8 88.7 74.1 72.4 74.0 77.8 71.2 e9.7 78.6 78.1 69.7 67.6 78.4 70.4 69.1 06.8 78.8 6!.9 68.1 es.4 78.8
100
R ~ A T R C, I
AIL
- ~ ,l- ~ ~ . -
0
61).O
!vi E
~ . --i.-
I A
62.7 62.S 62.2 62.0 611.0
.
860
5
...
91.9 79.6 67.1 6t.8 ~.
2.9 0
Mm. H g y PC. loo w,o -..
200 Mm. Hg
s
88.8 64.8
90.8
62.8 62.' 7 62.7 62.7 S7.0
78.2 70.1 69.8 70.0 67.8
0
81.8 77.7 6i.4
8.8
o
.At.0 :;
Two pbraw in liquid.
PC.
y
41.6
82.6 76.8 76.0 72.6 72.2 70.9
303
40.6 40.0 89.9 89.8 89.9 41.8 66.4
8
ACKNOWLEDGMENT
Appreciation is expressed to Salvatore J. Sivis, o Sidney Seff, and Murray H.W o n for the determine tion of experimental data reported; andtocarbide and Carbon Chemicals Corporation for supplying many of the solvents used. The suggestions made by H. C. Carlson in the organisation of the manuscript were most helpful.
TABLEVIII. VAPORCOMPOSITION DATAFOB METHYLETHYL KETONBI-WATER 8ysmMs AT Vharoue PRESSURES (SMOOTHQD DATA)
760 Mm. H g 5
0
8
6 10 20
so
40
60 60 70 80 90 100
y
0 61.1 64.6 66.1
66.1 66.1 66.1 66.1 66.2 66.2 69.6 78.4 100.0
PC. 100.0 77.0 78.4 78.2 73.2 73.2 78.2 78.2 73.2 78.8 78.6 76.2 79.6
500 Mm. H g y t'C. 88.6 0
64.0 67.7 68.0
66.7 62.3 62.0
68.0 68.0
62.0
62.0 68.0 62.0 68.0
68.0 68.8 72.1 80.4 100.0
62.0
62.0 62.1 62.2 68.8 66.8
840 Mm. He y
tOC.
0 67.2 69.6 70.0 70.0 70.0 70.0 70.0 70.0 70.4 78.8 81.1 100.0
79.6 16.6 63.0
62.8 62.8 62.3 42.8 62.8 62.8 62.4 62.9 63.9 66.0
200 Mm. Rg y
0 69.S 62.1 72.0 72.0 72.0 72.0 72.0 72.0 72.7 75.8 82.0 100,O
PC. 66.8 42.8 40.1 89.9 89.9 89.9 89.9 89.9 89.9 40.1 40.0 40.4 41.4
LITERATURE CITED
-201
0
I
I
I
I
I
I
I
I
10 20 30 40 5 0 60 70 80 Mote %Methyl Ethyl Ketone in Liquid
I
90 100
Figure 8. Difference of Vapor and Liquid Com~odtions W.S. Uquid Compositions (s)for Methyl KetoneWater
(y-s)
(1) Cornell, L. W., and Montonna, R. E., IND.ENO.'CHIDY., 25, 1331 (1933). (2) GiLnont, R.,and Othmer, D. F., Ibid., 36, 1061 (1944).
(3) Haurbrand, E., "Prinoiples and Practice of Industrial DintiIlation", 4th ed., New York, John Wiley & Sons, 1928. (4) International Critioal Tables, Vol. 111, p. 387, New York. Maraw-Hill Book Co., 1928. (6) Othmer, D. F., IND.ENO.CHmM., 35, 614 (1943). (6) Othmer, D. F., IND.ENO.CHIDW., ANAL.ED,, 4, 232 (1932). (7) Othmer, D. F., sndGiiont, R., IND.ENO.Cxrnm.,36,868 (1944). (8) SheU Chemical Co., Methyl Ethyl &tone Data Book, 1938.
Vapor Pressure of Liquid Nitric Acid The vapor p r e ~ ~ u of r eliquid (100%)nitric acid was calculeted from thermodynamic data on the assumption that the fugacity and vapor preaure are equal. The calculated values agreed well w i t h experimental data recently reported in the literature. The free energy equation for the vaporization of liquid nitric acid was found to be: 14,744 22.07TlnT 13.38 X 10-8 T" 166.26T AP
+
-
-
The boiling point of liquid nitric acid calculated from this equation is 84' C. Equations for the heat capacity of liquid and gaseous nitric acid were developed.
F
ORSYTHE and Giauque (a) recently published extensive thermodynamic data for nitric acid. They reported the heat capacities of liquid (1000/0)nitric acid and the heat contents of gaseous nitric acid; they calculated the free energy of formation
EDWARDP. EGAN, JR. Tennesw Valley Authority, Wibon Dam, Ala.
of gaseous nitric acid a t 298.1' IC. on the basis of the free energy of formation of liquid nitric acid and the vapor pressure data of Wilson and Miles (6),which on extrapolation gave 02.9 mm. of mercury as the vapor premure at 25' C. Forsythe and Giauque suggested but did not make the calculation of the fugacity of niMc acid from the data they presented. The wartime demand for concentrated nitric acid has added practical significance to the theoretical interest in the vapor pressure of this acid. If the assumption is made that the fugacity of nitrig acid is equal to the vapor pressure, the calculated fugacities can be compared directly with measured vapor pressures.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
Vol. 37, No. 3
tions for liquid and gaseous nitric acid, the calculated value for AH;, and the free energy of vaporization of nitric acid at 298.1" IC., the following equation for the free energy of vaporization was derived:
HN08 (liquid) = "Os A F O = 14,744
Figure 1. Vapor Pressure of Liquid Nitric Acid
The published data on vapor pressures of nitric acid and its aqueous solutions were compiled by Taylor (6) in 1925, and these data appear in the International Critical Tables (3). Taylor (5) reported that the data for solutions containing more than 70% nitric acid and for 100% (liquid) nitric acid were rather limited and inconsistent. Since 1925 a few data on the vapor pressure of liquid nitric acid have appeared; Wilson and Miles (6) made accurate measurements between 0' and 20' C., Klemenc and Rupp (4) made a few measurements in their study of the system HNOrNOzl and Berl and Saenger (I) reported the boiling point of nitric acid as 83" C. at 760 mm. of mercury pressure. The present paper gives heat capacity equations for liquid and gsreous nitric acid, an equation for the free energy of vaporization of nitric acid, and vapor pressure v,alues calculated from the free energy equation on the assumption that the fugacity and vapor pressure are equal. The calculations are based chiefly on the data of Forsythe and Giauque (2). The heat capacity equation for liquid nitric acid was derived from the measured heat capacities ( 2 ) . The equation for gaseous nitric acid was derived from calculated heat contents ( 2 ) ; M e r entiation of the resultant heat content equation yielded the heat capacity equation. The values calculated from the derived equations agreed with the values reported by Fonythe and Giauque (2) within about 0.1%. The heat capacities of liquid and gaseous nitric acid may be expressed by the following equations over the indicated temperature ranges:
- 8.0 X 1 O - T
(1)
+ 18.75 X 1 O - T
(2)
232' to 305°K.: C,(HNO,, liquid) = 28.64 275" to 500' K.: C,(HNOs, gas) = 6.57
Integration of the heat capacity equation for liquid nitric acid yielded the heat content equation:
(HO
- H,O)/T = 28.64 - 0.0042' ("Os,
liquid)
(3)
At 298.1O K. the value of (Ho - H$)/T is 27.45. The value of (HO - H X ) / T at 298.1' K. for gaseous nitric acid is 9.37 (2, Table XVII). The heat of vaporization a t 298.1" K., taken as the difference between the heats of formation of liquid and gaseous nitric acid ( Z ) , is 9355 calories per mole. Then, by the relation,
AH:
-T-
AHo =
-
A(Ho - HX)
T
(4)
AH: = 14,744 calories per mole of nitric acid vaporized a t 298.1" K. The free energy of vaporization at 298.1' K. is 1476 calories per mole (2). By combination of the heat capacity equa-
(gas)
(5)
+ 22.07T In T - 13.38 X 10-8 Tz - 166.26T
This equation is valid only at temperatures within the range of overlap between Equations 1 and 2 (275" to 305' K.) but can be, extrapolated to cover the temperature range 273. I' to 373.1" K. without the introcluction of significant error. At premnes near 1 atmosphere the fugacity of nitric acid probably would be a few per cent smaller than the measured vapor pressure. The fugacity, as calculated in terms of mm. of mercury from Equation 5, is given in Table I. In Table I1 and Figure 1 the fugacity and vapor pressure are assumed to be equal, and the calculated vapor pressures are compared with data from the literature. Table 11 shows that, although the calculated vapor pressure is higher than that reported by Taylor (6) near the extremes of the temperature range, the calculated values are in good general agreement with the values from the literature. The calculated boiling point from Equation 5 is 84' C., which agrees more closely with the value of 83" reported by Berl and Saenger (I) than with the value of 87' interpolated from the data of Taylor, particularly when allowance is made for the fact that the calculated fugacity is slightly lower than the true vapor pressure.
TABLE I. FUGACITY OF LIQUIDNITRICACID T,e K.
AFa
K,Atm.
f, Mm. H g
273.1 283.1 293.1 303.1 313.1 323.1 333.1 343.1 353.1 363.1 373.1
2,153 1.879 1,609 1,345 1,085 830 579 332 89 - IS1 388
0.019 0.035 0.063 0.107 .O. 175 0.274 0.417 0.615 0.882 1.233 1.687
14.4 26.6 47.9 81.3 133 208 317 467 670 937 1282
TABLE
-
11. COMPARISON BETWEEN CALCULATED AND EXPERIVAPORPRESSURES OF LIQUIDNITRICACID
MENTAL r
T, C.
Vapor Pressure, Mm. Hg Berl & Wilson Klemeno Saenger & Miles & Rupp (1) (6) (4) 14.0 14.7 14.9 20.1 19.6 26.5 27.1 31.5c 35.5 36.2 ... 47.3 48.0 61.0 62.9 62.1 77.4
Calod.n 0 14.4 5 19.7b 10 26.6 15 35.7b 47.8 20 62.5b 25 81.3 30 40 133 208 *. 50 ... 60 317 70 467 670 80 90 937 100 1282 730b 760 83 84 760b 87 856b a Fugacity and vapor pressure sasumed to be equal. b From Figure 1. 0 Temperature, 1 2.5' C.
..* ... ... ... ... ... ...
...
.. .. ...... ..
.... .. ..
... ...
... ...
... ... ... ... ... ..* ... ... ...
Taylor (6)
11 15 22 30 42 57 77 133 215 320 460 625 820
700b 760b
LITERATURE ClTED
(1) Berl, E., and Saenger, H. H., Monatsh., 53-54, 1036-56 (1929). (2) Forsythe, W.R.,and Giauque, W. F., J . Am. Chem. SOC.,64, 48-61, 3069 (1942); 65,2479 (1943). (3) International Critical Tables, Vol. 111, p. 305. (4) Klemeno, A., and Rupp, J., 2. anorg. allgem. Chem., 194, 51-72
(1930). (5) Taylor, G.B., IND.ENG.CHEM., 17, 633-5 (1925). (6) Wilson, G.L., and Miles, F. D., Trans. Faradag Soc.. 36,356-63 (1940).
