Effect of concentration, pH, and ionic strength on the viscosity of solutions of a soil fulvic acid

Abstract

The influence of pH (3.0–8.0), ionic strength (0.005–0.10 M), and concentration (ca. 50–300 mg L−1) on the viscosimetric behaviour of solutions of a soil fulvic acid has been determined. The results show a complex influence of the concentration on the specific viscosity with maxima at about 80–100 mg L−1 and a minimum at 140–160 mg L−1. The viscosity is minimum at pH ca. 6 and decreases when the ionic strength increases. The results are interpreted by a rod-type model from which the dimensions of fulvic acid molecules are calculated. Key words: soil fulvic acids, viscosity, configurational changes.