where Δ Δ ρ ρ 0 = ρ ρ l , 0 − − ρ ρ v , 0 ; the subscript zero to the density denotes the value at two-phase coexistence. It can be shown that the difference between the location of the surface of tension and of the equimolar dividing surface proposed by Gibbs yields the value of the Tolman length: