Knudsen Cell Studies of the Vaporization of Samarium Dicarbide |
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Authors: | NORMAN D. STOUT CLARENCE L. HOENIG PAUL C. NORDINE |
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Affiliation: | Lawrence Radiation Laboratory, University of California, Livermore, California 94550;Department of Chemistry, University of Kansas, Lawrence, Kansas 66045 |
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Abstract: | The vapor pressure of SmC2 in equilibrium with graphite was measured by the Mnudsen effusion technique. Rates of weight loss from the cells were measured with an automatic recording balance. The apparent pressures varied with orifice size, and equilibrium pressures were calculated by extrapolation to zero orifice area. This work was combined with other studies to obtain log10 P(atm) = - 13.869 × 103/T + 3.752 (1300°-2050°K) for the Sm vapor pressure above SmC2-C. Estimates of S°298 and cp were made for SmC2, and δH°298 was calculated to be 72.0 ± 2 kcal/mol for the reaction SmC2(s) = Sm(g) + 2C(s). This value combined with δH°v, 298= 48.6 kcal/mol for Sm gives a δ°f298 for SmC2 of 23.4 ± 2 kcal/mol. |
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