\"An unsteady-state porous frit method of diffusion coefficient measurement, recently developed in this laboratory, was improved and expanded upon. The experimental technique has been refined and documented. The unsteady-state diffusion of an initially 0.5 N NaCl solution into pure water (effective diffusivity -1.480 x 10-5 cm2/sec) was employed as the calibration standard. An overall calibration precision of ±4% was obtained. Diffusion times of two hours or less were used for the non-aqueous diffusivity measurements. The validity of this measurement technique was confirmed by the agreement of the measured self-diffusion coefficient of n-heptane (25⁰C) with literature values.
A numerical simulation of the frit diffusion process was developed and permitted such effects as solvent withdrawal and concentration dependency of the diffusion coefficient to be studied. A method of evaluating the overall effective diffusivity of the sodium chloride calibration standard for the specific conditions employed in this study was also developed. A time-averaged solvent volume approximation was employed for the data analysis. Numerical simulation confirmed the validity of both the NaCl effective diffusivity and the solvent volume approximations.
Diffusivities of a number of n-alkane-n-alkane and n-alkane-n-alcohol systems were measured at temperatures of 20⁰, 25⁰, 30⁰ and 40⁰C. A carbon-14 tracer technique was used in conjunction with the frit method. In most cases diffusivities were determined as the average of duplicate experimental measurements; agreement of the two measurements was generally ±10%.
The measured diffusivities permitted an investigation to be made concerning the diffusion mechanism of straight-chain molecules. Comparison of the data with the Stokes-Einstein and Eyring diffusion models indicated that during diffusion n-alkane molecules are oriented lengthwise parallel to the direction of flow. The group Dμ/T was found to be constant for the n-alkanes but showed a marked temperature dependence for the n-alkane-n-alcohol systems. Contrary to a previously proposed theory, the data indicated that the ratio of n-alkane diffusivities in an n-alkane solvent is not equal to the inverse ratio of solute carbon numbers.
The data were compared to numerous prediction correlations. Several correlations were found to be reasonably accurate for n-alkane diffusion. With the exception of one modified Eyring expression, all correlations failed to predict the n-alkane-n-alcohol diffusivities with any degree of accuracy. A previously unreported failing of an accepted diffusivity prediction relation was observed for this class of binary systems\"--Abstract, pages ii-iii.
","abstract_html":"<p>"An unsteady-state porous frit method of diffusion coefficient measurement, recently developed in this laboratory, was improved and expanded upon. The experimental technique has been refined and documented. The unsteady-state diffusion of an initially 0.5 N NaCl solution into pure water (effective diffusivity -1.480 x 10<sup>-5</sup> cm<sup>2</sup>/sec) was employed as the calibration standard. An overall calibration precision of ±4% was obtained. Diffusion times of two hours or less were used for the non-aqueous diffusivity measurements. The validity of this measurement technique was confirmed by the agreement of the measured self-diffusion coefficient of n-heptane (25⁰C) with literature values.</p> <p>A numerical simulation of the frit diffusion process was developed and permitted such effects as solvent withdrawal and concentration dependency of the diffusion coefficient to be studied. A method of evaluating the overall effective diffusivity of the sodium chloride calibration standard for the specific conditions employed in this study was also developed. A time-averaged solvent volume approximation was employed for the data analysis. Numerical simulation confirmed the validity of both the NaCl effective diffusivity and the solvent volume approximations.</p> <p>Diffusivities of a number of n-alkane-n-alkane and n-alkane-n-alcohol systems were measured at temperatures of 20⁰, 25⁰, 30⁰ and 40⁰C. A carbon-14 tracer technique was used in conjunction with the frit method. In most cases diffusivities were determined as the average of duplicate experimental measurements; agreement of the two measurements was generally ±10%.</p> <p>The measured diffusivities permitted an investigation to be made concerning the diffusion mechanism of straight-chain molecules. Comparison of the data with the Stokes-Einstein and Eyring diffusion models indicated that during diffusion n-alkane molecules are oriented lengthwise parallel to the direction of flow. The group Dμ/T was found to be constant for the n-alkanes but showed a marked temperature dependence for the n-alkane-n-alcohol systems. Contrary to a previously proposed theory, the data indicated that the ratio of n-alkane diffusivities in an n-alkane solvent is not equal to the inverse ratio of solute carbon numbers.</p> <p>The data were compared to numerous prediction correlations. Several correlations were found to be reasonably accurate for n-alkane diffusion. With the exception of one modified Eyring expression, all correlations failed to predict the n-alkane-n-alcohol diffusivities with any degree of accuracy. A previously unreported failing of an accepted diffusivity prediction relation was observed for this class of binary systems"--Abstract, pages ii-iii.</p>","abstract_has_math":false,"creators":["Moore, James W."],"institution":"University of Missouri--Rolla","degree_name":"Ph. D. in Chemical Engineering","degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2016,"date_issued":"2016-02-10T08:00:00Z","date_published":"2016-02-10T08:00:00Z","updated_at":"2026-07-24T03:19:30Z","subjects":["Chemical Engineering"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://scholarsmine.mst.edu/doctoral_dissertations/231","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Moore, James W."]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.available","label":"Dc Date Available","values":["2016-02-10T08:00:00Z"]},{"key":"dc:type","label":"Dc Type","values":["Dissertation - Open Access"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph. D. in Chemical Engineering"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Missouri--Rolla"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Chemical Engineering"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://scholarsmine.mst.edu/doctoral_dissertations/231"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["\"An unsteady-state porous frit method of diffusion coefficient measurement, recently developed in this laboratory, was improved and expanded upon. The experimental technique has been refined and documented. The unsteady-state diffusion of an initially 0.5 N NaCl solution into pure water (effective diffusivity -1.480 x 10-5 cm2/sec) was employed as the calibration standard. An overall calibration precision of ±4% was obtained. Diffusion times of two hours or less were used for the non-aqueous diffusivity measurements. The validity of this measurement technique was confirmed by the agreement of the measured self-diffusion coefficient of n-heptane (25⁰C) with literature values.
A numerical simulation of the frit diffusion process was developed and permitted such effects as solvent withdrawal and concentration dependency of the diffusion coefficient to be studied. A method of evaluating the overall effective diffusivity of the sodium chloride calibration standard for the specific conditions employed in this study was also developed. A time-averaged solvent volume approximation was employed for the data analysis. Numerical simulation confirmed the validity of both the NaCl effective diffusivity and the solvent volume approximations.
Diffusivities of a number of n-alkane-n-alkane and n-alkane-n-alcohol systems were measured at temperatures of 20⁰, 25⁰, 30⁰ and 40⁰C. A carbon-14 tracer technique was used in conjunction with the frit method. In most cases diffusivities were determined as the average of duplicate experimental measurements; agreement of the two measurements was generally ±10%.
The measured diffusivities permitted an investigation to be made concerning the diffusion mechanism of straight-chain molecules. Comparison of the data with the Stokes-Einstein and Eyring diffusion models indicated that during diffusion n-alkane molecules are oriented lengthwise parallel to the direction of flow. The group Dμ/T was found to be constant for the n-alkanes but showed a marked temperature dependence for the n-alkane-n-alcohol systems. Contrary to a previously proposed theory, the data indicated that the ratio of n-alkane diffusivities in an n-alkane solvent is not equal to the inverse ratio of solute carbon numbers.
The data were compared to numerous prediction correlations. Several correlations were found to be reasonably accurate for n-alkane diffusion. With the exception of one modified Eyring expression, all correlations failed to predict the n-alkane-n-alcohol diffusivities with any degree of accuracy. A previously unreported failing of an accepted diffusivity prediction relation was observed for this class of binary systems\"--Abstract, pages ii-iii.
"]},{"key":"dc:title","label":"Title","values":["Measurement of molecular diffusivities of liquid alkane systems"]}]}],"canonical_facts":{"dc:creator":["Moore, James W."],"dc:date.available":["2016-02-10T08:00:00Z"],"dc:description.abstract":["\"An unsteady-state porous frit method of diffusion coefficient measurement, recently developed in this laboratory, was improved and expanded upon. The experimental technique has been refined and documented. The unsteady-state diffusion of an initially 0.5 N NaCl solution into pure water (effective diffusivity -1.480 x 10-5 cm2/sec) was employed as the calibration standard. An overall calibration precision of ±4% was obtained. Diffusion times of two hours or less were used for the non-aqueous diffusivity measurements. The validity of this measurement technique was confirmed by the agreement of the measured self-diffusion coefficient of n-heptane (25⁰C) with literature values.
A numerical simulation of the frit diffusion process was developed and permitted such effects as solvent withdrawal and concentration dependency of the diffusion coefficient to be studied. A method of evaluating the overall effective diffusivity of the sodium chloride calibration standard for the specific conditions employed in this study was also developed. A time-averaged solvent volume approximation was employed for the data analysis. Numerical simulation confirmed the validity of both the NaCl effective diffusivity and the solvent volume approximations.
Diffusivities of a number of n-alkane-n-alkane and n-alkane-n-alcohol systems were measured at temperatures of 20⁰, 25⁰, 30⁰ and 40⁰C. A carbon-14 tracer technique was used in conjunction with the frit method. In most cases diffusivities were determined as the average of duplicate experimental measurements; agreement of the two measurements was generally ±10%.
The measured diffusivities permitted an investigation to be made concerning the diffusion mechanism of straight-chain molecules. Comparison of the data with the Stokes-Einstein and Eyring diffusion models indicated that during diffusion n-alkane molecules are oriented lengthwise parallel to the direction of flow. The group Dμ/T was found to be constant for the n-alkanes but showed a marked temperature dependence for the n-alkane-n-alcohol systems. Contrary to a previously proposed theory, the data indicated that the ratio of n-alkane diffusivities in an n-alkane solvent is not equal to the inverse ratio of solute carbon numbers.
The data were compared to numerous prediction correlations. Several correlations were found to be reasonably accurate for n-alkane diffusion. With the exception of one modified Eyring expression, all correlations failed to predict the n-alkane-n-alcohol diffusivities with any degree of accuracy. A previously unreported failing of an accepted diffusivity prediction relation was observed for this class of binary systems\"--Abstract, pages ii-iii.
"],"dc:identifier":["https://scholarsmine.mst.edu/doctoral_dissertations/231"],"dc:subject":["Chemical Engineering"],"dc:title":["Measurement of molecular diffusivities of liquid alkane systems"],"dc:type":["Dissertation - Open Access"],"thesis:degree_name":["Ph. D. in Chemical Engineering"],"thesis:institution_name":["University of Missouri--Rolla"]},"updated_at":"2026-07-24T03:19:30Z"}