When dealing with the case of concentrated systems, the zeta potential can be determined through measurement of the sedimentation potential E s , from the potential difference relative to the distance between the electrodes. The other parameters represent the following: η η the viscosity of the medium; λ λ the bulk conductivity; ε ε r the relative permittivity of the medium; ε ε 0 the permittivity of free space; ρ ρ the density of the particle; ρ ρ 0 the density of the medium; g is the acceleration due to gravity; and σ is the electrical conductivity of the bulk electrolyte solution.