So the molar flux of component i is (number of moles per unit time per unit area): j n , i = c i u i and the barycentric molar flux of component i is j n , i = c ( u i − − ⟨ ⟨ u ⟩ ⟩ ) , where ⟨ ⟨ u ⟩ ⟩ this time is the average molar velocity of all the components in the mixture, given by: ⟨ ⟨ u ⟩ ⟩ = 1 n ∑ ∑ i c i u i = 1 c ∑ ∑ i j n , i .