AbstractThe physicochemical properties of alkali lignin are crucial to its potential applications and recyclability, as it is one of the most important natural polymer materials. In this study, the solubility parameter (δ) of alkali lignin was determined using Hansen solubility parameters (HSP) theory and inverse gas chromatography (IGC). The δ of alkali lignin was determined by the IGC technique. Solute retention volumes (Vg0) of 6 solutes were determined using alkali lignin as the stationary phase. From 50 to 110 ºC, the δ of alkali lignin varied from 24.47 to 24.15 MPa1/2. Hansen solubility spheres were plotted using the data from the literature for the interactions of alkali lignin with 36 solutes to determine the three dimensional solubility parameter of alkali lignin at 25 to 100 ºC. These determined δ values were consistent with those calculated experimentally via IGC. Acetone was a moderate solvent for the alkali lignin.