In this study the author concentrated mainly on the characterisation of the physicochemical properties of β-humus fulvic acid fraction of selected types of soil against the background of humic acids, and tried to determine the role of that fraction in the determination of the sorptive properties of the soils. The paper presents results of the elementary composition as atomic percentages as well as by weight, and such indexes calculated on their basis as the H/C and C/N atomic ratios, and the degree of internal oxidation. Apart from those basic and fundamental analyses of humus compounds, the author presents also important physico-chemical parameters characterizing their structure and surface activity, such as the inner and outer specific surface area, molar energy of adsorption, and micro-porosity. The results obtained permitted the conclusion that β-humus preparations are characterized by considerable contamination in spite of their careful purification, which gives ground for the conclusion that β-humus is a permanent organic-mineral complex, occurring in soils under natural conditions in the form of a sediment, as a solid sorbent improving the sorptive properties of the soils. With relation to humic acids, β-humus displayed a higher content of active functional groups acting as adsorption centres and having a greater capacity of absorbing adsorbate particles on their surface, hence β-humus has greater specific surface area and molar energy of adsorption. The fraction showed also a lower degree of aromatisation, as compared to humic acids, and a greater number of lateral chains with stronger hydrophilic properties, hence the greater sorptive properties. Due to its specific properties, the presence of the fraction in soil results in a distinct improvement of the sorptive and productive properties of the soil.