 |
| Titel |
How many carboxyl groups does an average molecule of humic-like substances contain? |
| VerfasserIn |
I. Salma, G. G. Láng |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 8, no. 20 ; Nr. 8, no. 20 (2008-10-17), S.5997-6002 |
| Datensatznummer |
250006410
|
| Publikation (Nr.) |
 copernicus.org/acp-8-5997-2008.pdf |
|
|
|
|
|
| Zusammenfassung |
| The carboxyl groups of atmospheric humic-like substances (HULIS) are of
special interest because they influence the solubility in water, affect the
water activity and surface tension of droplets in the air, and allow
formation of chelates with biologically active elements. Experimentally
determined abundances of the carboxyl group within HULIS by functional group
analysis are consistent with our knowledge on the average molecular mass of
HULIS if the number of dissociable carboxyl groups is assumed to be rather
small. The best agreement between the average molecular mass derived from
the existing abundance data and the average molecular mass published earlier
occurs for assuming approximately one dissociable carboxyl group only. This
implies that HULIS can not be regarded as polycarboxilic acid in diluted
solutions. The average molecular mass of HULIS derived from our
electrochemical measurements with the assumption of one dissociable carboxyl
group or equivalently, one dissociable sulphate ester per molecule ranges
from 250 to 310 Da. It was concluded that HULIS are a moderately strong/weak
acid with a dissociation constant of about pK=3.4, which fits well into the
interval represented by fulvic and humic acids. The mean number of
dissociable hydrogen (i.e. of carboxyl groups and sulphate esters jointly)
in HULIS molecules was refined to be between 1.1 and 1.4 in acidic
solutions. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|