70. Solving a chemistry problem

11(II). Calculate the thickness of the surface layers δ of aluminum hydroxide sol particles if the specific surface Ssp, mass concentration c and sol viscosity η are known (see table). The particles have a spherical shape, the density of the dispersed phase and the dispersion medium are 2.4 and 1.0 g/cm3, respectively, and the viscosity of the dispersion medium is η0 = 1 mPa*s.
N version Ssp, m2/g s, % (wt) η , mPa*s
II 100.0 20 1.765