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Investigation of metastable zone width of ammonium oxalate aqueous solutions
Author(s) -
Sangwal K.,
Wójcik K.
Publication year - 2009
Publication title -
crystal research and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0232-1300
DOI - 10.1002/crat.200800545
Subject(s) - nucleation , supersaturation , metastability , saturation (graph theory) , supercooling , aqueous solution , chemistry , oxalate , thermodynamics , ammonium oxalate , classical nucleation theory , inorganic chemistry , physics , mathematics , organic chemistry , combinatorics
The metastable zone width of pure ammonium oxalate aqueous solutions, as represented by maximum supercooling Δ T max , is investigated as functions of cooling rate R and saturation temperature T 0 by the polythermal method. The experimental results are discussed by using two recently advanced approaches: (1) self‐consistent Nývlt‐like approach based on a power‐law relationship between nucleation rate J and maximum supersaturation ln S max , and (2) a novel approach based on the relationship between J and ln S max described by the classical three‐dimensional nucleation theory. Analysis of the experimental data revealed that both approaches describe the experimental data on metastable zone width by the polythermal method reliably and provide useful information about the physical processes and parameters involved in nucleation kinetics. The values of various physical quantities predicted by both of these approaches are reasonable for a fairly‐soluble compound. A careful examination of the data on Δ T max as a function of T 0 obtained by polythermal method and from density measurements showed that Δ T max has a slight tendency to decrease with increasing saturation temperature T 0 . The values of ln S max at saturation temperature 303 K suggest that the metastable zone width of ammonium oxalate aqueous solutions is determined by primary nucleation in the polythermal method and by secondary nucleation during density measurements. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)