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Knudsen Cell Studies of the Vaporization of Samarium Dicarbide
Author(s) -
STOUT NORMAN D.,
HOENIG CLARENCE L.,
NORDINE PAUL C.
Publication year - 1969
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1969.tb11201.x
Subject(s) - vaporization , knudsen number , body orifice , extrapolation , analytical chemistry (journal) , samarium , vapor pressure , chemistry , volatilisation , thermodynamics , materials science , inorganic chemistry , physics , chromatography , organic chemistry , mathematics , ecology , mathematical analysis , biology
The vapor pressure of SmC 2 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 log 10 P(atm) = ‐ 13.869 × 10 3 /T + 3.752 (1300°‐2050°K) for the Sm vapor pressure above SmC 2 ‐C. Estimates of S° 298 and c p were made for SmC 2 , and δH° 298 was calculated to be 72.0 ± 2 kcal/mol for the reaction SmC 2 (s) = Sm(g) + 2C(s). This value combined with δH° v, 298 = 48.6 kcal/mol for Sm gives a δ° f298 for SmC 2 of 23.4 ± 2 kcal/mol.