INDUSTRIAL AND ENGINEERING CHEMISTRY
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vergence pressure is much greater in amount than is the usual difference between the ideal equilibrium constants and the values which may be computed from Rsoult’s law. The relations outlined are fundamentally sound and can be considered reliable in case of all binary mixtures. They also appear to be a good approximation to the equilibrium relations between vapors and liquids of complex mixtures. The major difficulty is the correct estimation of the convergence pressure. For most engineering calculations, particularly where the working pressure is less than 50 per cent of the estimated convergence pressure, satisfactory results can be obtained without the necessity of making careful calculations to determine the convergence pressure. I n such cases the convergence pressure can be estimated with sufficient accuracy from the critical pressure of the mixture itself and from estimates of critical pressures of other similar mixtures. Literature Cited (1) Brown, Petroleum Engr., 11, No. 8 , 25 (1940). (2) Ibid., 11, No. 9, 55 (1940). (3) Brown and Caine, Trans. Am. Inst. Chem. Engrs., 21, 91 (1928). (4) Cummings, Stone, and Volante, IND.ENG.CHEM., 25,728 (1933). (5) Gilliland and Scheeline, Ibid., 32, 48 (1940).
Temperature
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Vol. 34, No. 10
Huntington and Brown, Ibid., 29, 1408 (1937). K a t i and Brown, Ibid., 25, 1373 (1933). Kats and Hackmuth, Ibid., 29, 1073 (1937). Kats and Kurata, Ibid.. 32, 817 (1940). (10) Kay, Ibid., 30, 459 (1938). (11) Z b X , 32, 353 (1940). (12) Konz and Brown, Ibid., 33, 617 (1941). (13) Matheson and Cummings, Ibid., 25, 723 (1933). (14) Nysewander, Sage, and Lacoy. Ibid., 32, 118 (1940). (1 5) Perry. Chemical Engineers’ Handbook, New York, McGrawHill Book Co., 1934. (16) Piroomov and Beiswenger, Am. Petroleum Inst., Bull. 10,No. 2 , 52 (1929). (17) Podbielniak, IND. ENG.CHEM.,ANAL.ED., 5, 135 (1933). (18) Podbielniak and Brown, IND.ENQ.CHEM., 21, 773 (1929). (19) Rogers and Brown, Trans. Am. Inst. Chem. Engrs., 22, 107 (1929). (20) Sage, Hicks, and Lacey, “A. P. I. Drilling and Production Praotice”, p. 435 (1939). (21) Sage and Lacey, IND. ENO.CHEM.,32, 992 (1940). (22) Sage, Lacey, and Schaafsma, Ibid., 26, 214 (1934). (23) Scheeline and Gilliland, Ibid., 31, 1050 (1939). (24) Smith and Watson, Ibid., 29, 1408 (1937). (25) Souders, Selheimer, and Brown, Ibid., 2 4 , 5 1 7 (1932). (26) Universal Oil Products Co., “Laboratory Test Methods for Petroleum and Its Products”. p. 30 (1937). PRESENTBD before the Dividon of Petroleum Chemistry at the 104th N e e t ins of the A X E R I C A N CHEMICAL SOCIETY, Buffalo, N. Y. (6) (7) (8) (9)
Cr/t /ca/ Temperature
oc.
OK
Nomograph for Calculating Reduced Temperatures D. S . DAVIS Wayne University, Detroit, Mich.
EDUCED temperature, the ratio of the absolute temperature of a substance to its absolute critical temperature, has sufficient thermodynamic application to warrant the construction and use of a nomograph for its calculation. The accompanying alignment chart covers temperatures, critical and otherwise, in centigrade and Fahrenheit units and indicates the critical temperatures for eighteen pure gases and air. The index line shows that the vahic! of the reduced temperature for hexane a t 68’ C. is 0.67.
