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Supersaturated Electrolyte Solutions: Theory and ExperimentHighly supersaturated electrolyte solutions can be prepared and studied employing an electrodynamic levitator trap (ELT) technique. The ELT technique involves containerless suspension of a microdroplet thus eliminating dust, dirt, and container walls which normally cause heterogeneous nucleation. This allows very high supersaturations to be achieved. A theoretical study of the experimental results obtained for the water activity in microdroplets of various electrolyte solutions is based on the development of the Cahn-Hilliard formalism for electrolyte solutions. In the approach suggested the metastable state for electrolyte solutions is described in terms of the conserved order parameter omega(r,t) associated with fluctuations of the mean solute concentration n(sub 0). Parameters of the corresponding Ginzburg-Landau free energy functional which defines the dynamics of metastable state relaxation are determined and expressed through the experimentally measured quantities. A correspondence of 96-99 % between theory and experiment for all solutions studied was achieved and allowed the determination of an analytical expression for the spinodal concentration n(sub spin), and its calculation for various electrolyte solutions at 298 K. The assumption that subcritical solute clusters consist of the electrically neutral Bjerrum pairs has allowed both analytical and numerical investigation of the number-size N(sub c) of nucleation monomers (aggregates of the Bjerrum pairs) which are elementary units of the solute critical clusters. This has also allowed estimations for the surface tension Alpha, and equilibrium bulk energy Beta per solute molecule in the nucleation monomers. The dependence of these properties on the temperature T and on the solute concentration n(sub 0) through the entire metastable zone (from saturation concentration n(sub sat) to spinodal n(sub spin) is examined. It has been demonstrated that there are the following asymptotics: N(sub c), = I at spinodal concentration and N(sub c) = infinity at saturation.
Document ID
19970020724
Acquisition Source
Marshall Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
doi:10.1103/PhysRevE.52.3923
Authors
Izmailov, Alexander F. (Polytechnic Univ. Brooklyn, NY United States)
Myerson, Allan S. (Polytechnic Univ. Brooklyn, NY United States)
Na, Han-Soo (Polytechnic Univ. Brooklyn, NY United States)
Date Acquired
September 6, 2013
Publication Date
October 1, 1995
Publication Information
Publication: Physical Review E
Publisher: The American Physical Society
Volume: 52
Issue: 4
ISSN: 1063-651X
Subject Category
Inorganic And Physical Chemistry
Report/Patent Number
NAS 1.26:204762
NASA-CR-204762
Accession Number
97N21977
Funding Number(s)
CONTRACT_GRANT: NSF CTS-90-20233
CONTRACT_GRANT: NAG8-960
CONTRACT_GRANT: NAG8-1060
Distribution Limits
Public
Copyright
Public Use Permitted.

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