Thermal Diffusion and Self-Diffusion in Ammonia

Abstract

The temperature dependence of the isotopic thermal-diffusion factor α0 for ammonia has been investigated with the help of an equimolar mixture of 14NH3 and 15NH3. A 10-tube metal swing-separator as well as a two-bulb glass apparatus were used for these measurements. The value of α0 increases with temperature, its value being 0.00±0.02 at 242°K to 0.09±0.03 at 496°K, in disagreement with the values obtained by Watson and Woernley, who observed a definite inversion in the sign of α0 at temperature ∼290°K. The present set of observed values of α0 also disagrees with the theoretical calculation of Monchick and Mason. Possible causes of this disagreement are: (1) inadequacy of the potential model, (2) neglect of inelastic collisions, and (3) formation of dimers. The self-diffusion coefficient of ammonia has also been studied in the temperature range of 233° to 353°K with a two-bulb apparatus. There is marked disagreement between observed and calculated values at low temperatures. This is also explained in terms of dimerization.

Intermolecular forces in gaseous ammonia and in ammonia – nonpolar gas mixtures

“…Two sets of data are available for the selfdiffusivity of ammonia (46,47). Table 3 compares calculated values with experimental results (root mean square (r.m.s.)…”

Diffusivities in Binary Mixtures of Ammonia Dissolved in n-Hexane, 1-Hexanol, or Cyclohexane Determined by Dynamic Light Scattering and Molecular Dynamics Simulations

“…Besides the application-related use, mixtures consisting of polar NH 3 dissolved in systematically selected solvents are additionally of interest in connection with fundamental research with the objective of revealing influences of molecular characteristics on D 11 . So far, some experimental − and theoretical − studies are available for self-diffusion coefficients, also referred to as intradiffusion coefficients in the literature, of pure NH 3 or corresponding mixtures. Until now, however, only limited data are available for D 11 in gaseous mixtures with NH 3 or mixtures consisting of a liquid and dissolved NH 3 . − …”

Mutual-diffusion coefficients of some binary gas mixtures

“…[~2"I~ (3), [13] (4), [31] (5), and [32] (6). 4); the points correspond to the experimental values of [13] (I), [33] (2), [34] (3), [351 ( 4), (36) [5], [81 ( 6), [37] (7), [38] (8), [39] (9).…”