The effect of sodium dextran sulphate (M w  = 500,000) on the forced hydrolysis of FeCl 3 solutions was investigated using a microwave-assisted method. Reference samples obtained upon 10 to 120 min of forced hydrolysis of the FeCl 3 solution showed the presence of an α-Fe 2 O 3 phase alone. After 10 min of the forced hydrolysis of FeCl 3 in the solution containing sodium dextran sulphate, α-Fe 2 O 3 and additionally β-FeOOH precipitated. The Mössbauer spectra of α-Fe 2 O 3 precipitated in the presence of sodium dextran sulphate showed a significant broadening of spectral lines accompanied by decreased values of the hyperfine magnetic field. This was explained by lower α-Fe 2 O 3 crystallinity. The FESEM of reference α-Fe 2 O 3 samples showed cube-like particles of good uniformity in the submicrometer range. In the presence of dextran sulphate polymer, the α-Fe 2 O 3 particles of varying sizes and close to egg-like shape were obtained as a result of the specific adsorption of sulphates on the oxide surface and steric conditions created by dextran branches. Graphical abstract Right side : Effect of sodium dextran sulphate on the size and shape of α-Fe 2 O 3 particles produced by the forced hydrolysis of FeCl 3 solutions in the presence of microwave irradiation; Left side : reference α-Fe 2 O 3 particles.