COLLOID-SIZE GLOBULES OF HUMIC SUBSTANCES
Abstract
A study was made on disperse systems formed by soluble salts of humic acids for the clarification of the conditions under which the transition of the colloidal states of humic substances takes place. Low alkalinity (pH, 7 to 8) converts humic substances into a predominantly H+ form, which is formed in the shape of globular micelles with a hydrophilic shell. The spherical shape of the particles is due to the presence of numerous H- bonds between the macromolecules. In the Na humates studied an increase in pH by addition of an alkali causes the exchange of H+ ions for Na+ ions with a resultant unfolding of the globular micelles, peptization, and reduction in the average molecular weight. A sharp increase in viscosity also occurs with increased pH in consequence of the further gel formation which follows. The system thereby becomes thixotropic. The introduction of polyvalent ions, such as Ca++ or Fe+++, causes a reduction in solubility, which, with sufficiently complete ion exchange, can be followed by the precipitation of a solid-like gel with a network structure. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- May 25, 1961
- Accession Number
- AD0257924
Entities
Organizations
- Library of Congress