INDUSTRIAL AND ENGINEERING CHEMISTRY
438
VOL. 32, NO, 3
Gas Phase
Results on this phase are given in Table I and are plotted in Figure 6, where the mole fraction of $320 benzene in the gas phase (1 - y) is given as a function of the pressure for different temperatures. For k240 comparison, the values of Lewis and Luke (8) a t 100" and 125' C. for the two pressures of 75 and 2 98 atmospheres are also shown. A complete lack w" 160 of agreement between the two sets of data is found, their values being about 15 per cent lower than those of the present authors. No explanation for this disagreement can be suggested. As previously noted, Lewis and Luke measured the gas- and liquidphase compositions by independent experiments; MOL FRACTION OF NITROGEN they used a static method for the liquid phase and a dynamic method for the gas phase. Hence this lack of agreement in the gas-phase data has no bearing on the systems, such as methane-propane ( 1 1 ) , where the critical agreement found in the case of the liquid phase. conditions of the two components are not far apart. In such Figure 6 shows that a t all three temperatures the mole cases the divergence between the critical and cricondentherm fraction of benzene goes through a minimum. The pressure pressures is not large. However, complete data for a system a t which this occurs increases with temperature, from apof components as dissimilar as nitrogen and benzene have not proximately 140 atmospheres a t 75" C. to about 180 atmosbeen reported. The occurrence of the cricondentherms a t pheres a t 125" C. This behavior, while unusual, was also such relatively low pressures for nitrogen-benzene indicates observed by Pollitzer and Strebel (9) in the case of carbon the great qualitative difference that may be expected between dioxide-nitrogen at -51.6" C., in which case a minimum the two types of system. This difference makes it desirable concentration of carbon dioxide was observed a t about 80 to carry the study of the benzene-nitrogen system and of atmospheres. I n this connection it may be of some signifisimilar systems to higher pressures, in order to secure a knowlcance that carbon dioxide a t -52" C. is a t approximately the edge of the critical conditions over a t least part of the composame reduced temperature as benzene a t 125" C. On the sition range. other hand, Bartlett ( 1 ) found that the water vapor content of compressed nitrogen and hydrogen decreases with increase Literature C i t e d of pressure all the way up to 1000 atmospheres, the curves (1)-Bartlett, E. P., J. Am. Chem. Sot., 49,65 (1927). showing a tendency to flatten out a t the higher pressures. (2) Dodge, B. F., and Dunbar, A. K.9 Ibid.,49,591 (1927). Similar behavior Over the same pressure range was observed (3) Frolich, K.,Tauch. E. J., Hogan, J. J., and Peer, A. A., IND. for the system ammonia-nitrogen-hydrogen by Larson and EIFQ.CHEM.,23, 548 (1931). Black (7). (4) Goodman, J. B.,and Krape, N. W., Ibid.,23, 401 (1931). (5) International Critical Tables, Vol. 111, p, 254, New York, T h e probable hlcGraw-Hill Book Co. (1928). significance of (6) Larson, A. T., and Black, C. A., IND. ENQ. CHEM.,17, 715 t h e s e minima is (1925). seen more Clearly (7) Larson, A. T., and Black, C. A., 2. Am. Chem. SOC.,47, 1015 from Figure 7, in (1925). (8) Lewis, 1 %'. K., and Luke, c. D., IND. ENO.CHEM.,25,725 (1933). which the (9) Pollitzer, F.,and Strebel, E., 2. physik. Chem., 110,768 (1924). Of Figures and (10) Saddington, A.W., and Krase, N. W., J . Am. Chem. SOC.,56,353 h a v e been com(1934). (11) Sage, B. H.,Larey, W. H., and Schaafsma, J. G., IND.ENQ. bined t o give a CHEM.,26, 214 (1934). phase d i a g r a m . (12) Wan, Shen-wu, and Dodge, B. F., Ibid.,32,95 (1940). Since t h e d a t a (13) Wiebe, R.,and Gaddy, V. L., J . Am. Chem. SOC.,56, 76 (1934). cover onlv a small p o r t i o n of t h e T H Ipaper ~ is based on a dissertation presented by Philip Miller in June, 1938, composition range to the faculty of the Engineering School of Yale University, in aandidacy for the degree of doctor of engineering. from pure benzene to pure nitrogen, t h e y c a n serve only to help us guess a t the posEngineering i n the Service of PRESSURE IN ATMOSPHERES sible form of the Chemistry-Correction complete diagram, In the article published in January, 1940, pages 23 to 31, as indicated in the smal' insert. However, the pressure of minicorrections should be made as follows: The equation attributed mum concentration of benzene in the gas phase corresponds t o to von Karman, column 1, page 29, should read: the cricondentherm, one of the critical points exhibited by all binary systems. It is the point of maximum concentration of the more volatile component, beyond which no condensation will occur a t any pressure, The occurrence of this minimum is, then, no longer surprising, although the relatively low pressure a t which it occurs is perhaps unexpected, since any The definition of the conversion factor on page 30 should read: plausible completion of the diagram will give a large gap belb. (mass) X ft. tween critical and cricondentherm pressures. gc = Ib. (force) X hr.* The only cases in which isotherms have been determined T.H. CHILTON over the entire composition range are those of hydrocarbon
