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INDUSTRIAL AND ENGINEERING CHEMISTRY
2. The activity coefficients of any gas whose BeattieBridgeman constants are known may be calculated readily a t any desired temperature and pressure by means of Equation 9 with a satisfactory degree of accuracy up to pressures of 200-300 atmospheres and for temperatures at least as low as T, = 1.5. At higher temperatures satisfactory agreement between calculated and observed values can be obtained for the gases studied up to 500 atmospheres. 3. Satisfactory agreement between observed and calculated values of the activity coefficients of gases may be obtained a t temperatures considerably higher than those for which given Beattie-Bridgeman constants have been evaluated. 4. From the coefficients of Equation 9 for the various gases present in a n equilibrium, a n analytic expression for log,, K , as a function of P and T may be readily obtained which will be accurate in the same pressure range as the activity coefficients of the constituent gases. 5 . The outlined method of calculation of activity coefficients has the advantage over other methods suggested so far in that log y and log K , are obtained analytically as functions of P and T rather than of V and T , and a t any desired temperature, within the specified limitations, provided the Beattie-Bridgeman constants for the gases in question are known.
KP
Vol. 33, No. 1
equilibrium expression for gases in terms of pressure only K7 = equilibrium activity coefficient ratio R-,H.~W. = activity coefficient ratios for ammonia synthesis a8 given by Hougen and Watson (9) P = pressure, atmospheres PO,PH,PD,PB = partial pressures of various gases present in an equilibrium mixture, atm. R = molar gas constant, cc.-:tm./’ K. T = absolute temperature, K. V = actual volume of gas, cc./mole Vi = ideal volume of gas, cc./mole p , y ~ , 6 = virial coefficients of Beattie-Bridgeman equation which are functions of T only for a given gas Y = activity coefficient of gas Y&d. = calculated activity coefficients YD.LB. = activity coefficients listed by Deming and Shupe (7,8) ?graph. = activity coefficients determined by graphical method Y G , Y X , Y D , 78 = activity coefficients of various gases present in an equilibrium mixture =
Literature Cited Bartlett, Cupples, and Tremearne, J . Am. Chem. Soc., 50, 1275 (1928). Beattie, Proc. Natl. Acad. Sci., 16, 14 (1930). Beattie and Bridgeman, J . Am. Chem. Soc., 50, 3133 (1928). Beattie and Bridgeman, Proc. Am. Amd. Arts Sci., 63, 229 (1928). Beattie and Lawrence, J . Am. Chem. SOC.,52, 6 (1930). Deming and Shupe, Ibid., 52, 1382 (1930). Deming and Shupe, Phw. Rev.,37, 638 (1931). Ibid., 40,848 (1932). Hougen and Watson, “Industrial Chemical Calculations”, 2nd ed., p. 454,New York, John Wiley & Sons, 1936. Keyes, J . Am. Chem. Soc., 53,965 (1931). Newton, IND.EIG. CHEM.,27, 302 (1936). Robinson and Bliss, I b i d . , 32, 396 (1940). Tenell, J . Phgls. Chem., 35, 2885 (1931).
Nomenclature a,b, c, Ao, Bo = Beattie-Bridgeman constants, for P in atmospheres and V in cc./mole f = fugacity, atmospheres k , I, m = coefficients in Equation 9, dependent only on temperature for a given gas K. = thermodynamic equilibrium constant
Film Continuity of Svnthetic Resin Coatings J
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Accelerated Film Breakdown Test G. H. YOUNG, G. W. GERHARDT, W. I
