Misra technique 1 applied to solidification of cast iron
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Experimental and Calculated Values of Tracer Diffusion in Mercury
D x 10 9, m~ s -~ Solute
~X~
T (K)
Experimental
Calculated
Data Source
Sb
3.22
Sn
3.24
TI
3.4
Zn
2.76
293 298 343 363 282.6 283.7 293 295 298 284.5 293 298 273 284.5 288 293 298 303 323 372.3
1.3 to 1.47 1.15 to 1.64 1.37 2.42 1.80 1.77 1.43 to 1.48 1.55 1.3 to 1.68 1.00 0.91 to 1.05 1.0 to 1.60 1.51 2.52 2.42 1.46 to 1.89 1.57 to 2.40 1.2 to 1.8 2.06 3.35
1.83 1.89 2.52 2.82 1.67 1.68 1.80 1.82 1.91 1.61 1.71 1.77 1.83 1.98 2.05 2.12 2.20 2.27 2.57 3.42
5 5 5 5 2, 5 5 5 5 2, 5 2, 5 5 2, 5 5 5 2, 5 2, 5 5 2, 5 5 5
Note: In cases where more than one experimental value has been reported at the same temperature, the range is given here.
high temperatures. In assessing the comparison presented in this table, it should be borne in mind that the experimental values show considerable scatter and the errors of the order of 100 pct are not uncommon.13 For example, note the inconsistent trend and the wide scatter seen in the data for the diffusion of cadmium, silver, potassium, and sodium, e t c . Furthermore, the equation proposed herein has a deficiency in that it does not take into account the dissimilar valencies of the solute-solvent pair. There does not appear to be a simple way of incorporating this feature into the proposed equation at this stage. Despite these limitations, the discrepancy between the calculated and the actual values is generally not more than 100 pct, which is of the order of the uncertainty of experimental data; in many cases the two values are within 25 to 30 pct of each other. In view of this, therefore, the agreement between the calculated and measured values of diffusion coefficient is regarded to be satisfactory. In this work, a semitheoretical equation has been developed which allows the calculation of the metallic tracer diffusion coefficients in mercury as the solvent. The agreement between the actual and the calculated values of tracer diffusion coefficients is reasonable for a variety of solutes and over wide ranges of temperature; in some cases, however, the two values differ appreciably and possible reasons for this behavior have been outlined. Any further attempts to refine the equation proposed herein, we feel, should await more experimental work.
4. V. M . M . Lobo and R. Mills: Electrochimica Acta, 1982, vol. 27, pp. 969-71. 5. Z. Galus: Pure & Appl. Chem., 1984, vol. 56, pp. 635-44. 6. R.P. Chhabra and T. Sridhar: Phys. Chem. Liq., 1983, vol. 13, pp. 37-46. 7. J.H. Hildebrand: Viscosity and Diffusivity: A Predictive Treatment, Wiley-lnterscience, New York, NY, 1977. 8. E A. L. Dullien: Trans. Faraday Sot., 1963, vol. 59, p. 586. 9. R.P. Chhabra, T. Sridhar, P. H.T. Uhlherr, and O . E . Potter: A.I.Ch.E.J., 1980, vol. 26, pp. 522-25. 10. E A. L. Dullien: A.I.Ch.E.J., 1972, vol. 18, p. 62. 11. A.F. Crawley: Int. Met. Rev., 1974, vol. 19, pp. 32-48. 12. C.J. Smithells: Metals Reference Book, Bunerworths, London, 1967. vol. I, pp. 139-42. 13. J.R. Wilson: Met. Rev., 1965, vol. 13, pp. 381. 14. N.H. N
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