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| Titel |
Heterogeneous freezing of single sulfuric acid solution droplets: laboratory experiments utilizing an acoustic levitator |
| VerfasserIn |
M. Ettner, S. K. Mitra, S. Borrmann |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 4, no. 7 ; Nr. 4, no. 7 (2004-09-29), S.1925-1932 |
| Datensatznummer |
250002039
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| Publikation (Nr.) |
 copernicus.org/acp-4-1925-2004.pdf |
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| Zusammenfassung |
| The heterogeneous freezing temperatures of single binary sulfuric acid
solution droplets were measured in dependency of acid concentration down to
temperatures as low as -50°C. In order to avoid influence of supporting
substrates on the freezing characteristics, a new technique has been
developed to suspend the droplet by means of an acoustic levitator. The
droplets contained immersed particles of graphite, kaolin or montmorillonite
in order to study the influence of the presence of such contamination on the
freezing temperature. The radii of the suspended droplets spanned the range
between 0.4 and 1.1mm and the concentration of the sulfuric acid solution
varied between 5 and 14 weight percent. The presence of the particles in the
solution raises the freezing temperature with respect to homogeneous
freezing of these solution droplets. The pure solution droplets can be
supercooled up to 40 degrees below the ice-acid solution thermodynamic
equilibrium curve. Depending on the concentration of sulfuric acid and the
nature of the impurity the polluted droplets froze between -11°C and
-35°C. The new experimental set-up, combining a deep freezer with a
movable ultrasonic levitator and suitable optics, proved to be a useful
approach for such investigations on individual droplets. |
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