Among the tools used to describe the ramified structure or the rugged and distorted surface of humic acids (HA), fractal geometry seems to be one of the most adequate to explain the conformation of humic particles (molecular aggregates). From the experimental point of view, fractal dimension (D) of natural systems may be measured through the transmitted light, not scattered or absorved (turbidimetry'τ'). The presence of fractals indicates that the system may be decomposed in parts, each part being a copy of the whole. The determination of the fractal dimension (D) of these particles was achieved by the turbidimetric technique, where diluted solutions of commercial-HA and Espodossolo-HA were analyzed by spectrophotometry UV-Vis. The mathematical base used was the potential law τ ∝ λβ, where β < 3 indicates the presence of mass fractal (Dm); 3 < β < 4 of surface fractal (Ds) and β ≅ 3, of non-fractal (NF). The slope of the lines (β) was taken from the graphics (logτ vs logλ) to obtain D. The results show that the HA particles in diluted aqueous suspension form fractals structures, whose geometry may be characterized by turbidimetry. However, the wavelength range used (400 to 550 nm) is still small to make statements about the fractal nature of HA and determine its fractal dimensions with precision.
humic substances; conformation; turbidimetry