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Experimental determinations of diffusion coefficients in dilute aqueous solution using the method of hydrodynamic
M Z Southard1, L J Dias, K J Himmelstein
1Department of Chemical and Petroleum Engineering, University of Kansas, Lawrence 66045.
Pharmaceutical Research
|December 1, 1991
Summary
Diffusion coefficients were measured for various compounds in aqueous solution. Results show diffusivity depends on ionic state and molecular weight, impacting hydration and transport.
Area of Science:
- Physical Chemistry
- Solution Chemistry
- Transport Phenomena
Background:
- Diffusion coefficients are fundamental properties governing solute transport in solutions.
- Understanding diffusion is crucial for various chemical and biological processes.
- Experimental determination of diffusion coefficients requires precise methodologies.
Purpose of the Study:
- To experimentally determine diffusion coefficients in dilute aqueous solutions.
- To investigate the influence of ionic state and molecular weight on diffusion.
- To validate Taylor's method for measuring diffusion coefficients accurately.
Main Methods:
- Utilized Taylor's method of hydrodynamic stability for diffusion coefficient measurement.
- Employed a capillary tube setup to create stable concentration gradients.
- Measured solution densities using a tuning fork densimeter.
Main Results:
- Diffusion coefficients varied significantly with the ionic form of the solute.
- Diffusivity was influenced by the degree of ionization, likely due to changes in hydration.
- An unexpected dependency of diffusivity on molecular weight was observed for glycine series.
Conclusions:
- Taylor's method provides accurate measurements differentiating ionic forms.
- Solute charge and hydration state significantly impact diffusion in aqueous solutions.
- Molecular weight also plays a role in solute diffusivity, particularly for homologous series.