The solids concentration profiles in a mixing tank with mechanical agitation (axial flow impeller) have been measured using a light scattering technique associated with the refractive index matching procedure. Due to the high value of the refractive index of the particles, a new liquid mixture had been tested (70.2% beta-Pinen and 29.8% 1-methylnaphtalene, v/v). The experimental profiles are compared with similar measurements from the literature obtained with intrusive techniques. Additionally, simulated results calculated by the settling-dispersion model are also presented for further comparison.