n Q, 0 -4 0 --1.0--2.0 -3.0--4.0 -5.0-1.0 0-Th --.-.-: a / I( :/; "." 0 0.5 1.0 1.5 2.0 2.5 Log [ MOj Figure 1. Log D vs. log [MO] for metal extraction ("Os concn = 9.46N; O/A = 2.50; initial metal concn = 0.05M)To obtain the value of n in the above equation, extractions of " 0 3 were carried out as a function of the solvent concentration with solutions containing no metal ions. The results are given as a log D vs. log [MO] plot shown in Figure 2, where the slope of the best line is 1.18. The species (HN03.H20*MO) was either coextracted with the metal ions or could be formed first and then coordinated with the metal nitrates. In each of these experiments the acidity of the aqueous raffinate was practically the same as that of the corresponding experiment for the metal extraction. L o g [MO] Figure 2. Log D vs. log [MO] for "03 extraction ("03 concn = 9.46N; O/A = 2.50; initial metal concn = 0.05M) Although extraction of the metals is greater at higher "03 concentration and O/A value, the largest separation factor between thorium and yttrium ( D r r h / D Y ) , 84.4, occurred at a " 0 3 concentration of 9.46N and an O/A value of 1.25. The separation factor between yttrium and lanthanum ( D Y / D L~) was less than 1.2 in all cases.The Stefan method was used to measure the binary gaseous diffusion coefficients of n-pentane (nPe) in hydrogen, helium, nitrogen, air, and argon at 1 atm pressure and a temperature from -15" to 25°C at sec; nPe-He, 0.3044 f 0.0003 cm*/sec; nPe-Nz, 0.0885 f 0.0001 cm2/sec, nPe-air, 0.0877 * 0.0002 cm2/sec; and nPe-Ar, 0.0792 f 0.0007 cm2/sec. The 0.0885 f 0.0001 cm2/sec, 2nPe-air, 0.0877 0.0002 cm2/sec; and nPe-Ar, 0.0792 f 0.0007 cm2/sec. The temperature exponent for each system lay between 1.778 and 1.971, in good agreement with the predicted values based upon the Lennard-Jones force constants in the Chapman-Enskog approximate kinetic theory.Binary gaseous diffusion coefficients in hydrocarbon systems are important physical properties for chemical engineering. The temperature exponents of diffusion coefficients are also important for simplifying interpolation and (possibly) for extrapolation. There are relatively few such data in the literature, and those values differ in many cases. Therefore, we measured the diffusion coefficients by the Stefan method with hydrogen, helium, nitrogen, air, and argon as the carrier gases for n-pentane.
ExperimentalThe n-pentane was of pure grade (99 mol % minimum purity). The carrier gases-hydrogen, helium, nitrogen, air, and argon-were supplied by Hitachi Oxygen Co. (99.9 mol % minimum purity).The Stefan method was used for the determination of the binary gaseous diffusion coefficients. Since the experimental method is well known, only a brief description will be given here. The apparatus consisted of the diffusion cell (Figure l ) , which contained a capillary tube of 0.10-cm i.d., 0.60-cm o.d., and IO-cm length. The cell was immersed in a well-agitated water (or methanol solution) bath whose temperature was controlled to within 0.05"C. The temperature...
