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Knudsen and Langmuir Evaporation Studies of Stannic Oxide
Author(s) -
HOENIG C. L.,
SEARCY ALAN W.
Publication year - 1966
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.1151-2916.1966.tb15390.x
Subject(s) - enthalpy , chemistry , dissociation (chemistry) , langmuir , knudsen number , evaporation , molecule , crystallite , analytical chemistry (journal) , thermodynamics , crystallography , organic chemistry , adsorption , physics
A Knudsen study of the reaction SnO 2 ( c ) = SnO( g ) +½O 2 ( g ) yielded for the enthalpy of dissociation of SnO( g ), D° 0 = 5.44 × 0.1 ev/molecule, which is in agreement with literature values (average 5.5 × 0.1 ev/molecule) obtained by various methods. Langmuir studies indicated an evaporation coefficient upper limit of 0.1 for the measured reaction. The Langmuir enthalpy of activation (Δ H * 298 = 134 × 2.9 kcal/mole), as calculated by the second‐law method, is less than that measured for the equilibrium reaction (Δ H * 298 = 143.4 × 1.1 kcal/mole), but probably should be considered to agree within experimental error. Electron micrographs showed evidence of stepwise evaporation that depends on the crystallographic orientation of the polycrystalline grains.