Consider acetone and methanol diffusing concurrently through a stagnant air column. The mole fractions of all three components are obtained by solving the species balance equation augmented with the Stefan–Maxwell equations for the diffusion fluxes. The resulting nonlinear boundary value problem can be solved using either a shooting method or by implementing an orthogonal collocation technique. In this Demonstration we use both methods. The plot shows the steady state concentration profiles of the three species in the diffusion column. The solid curves were obtained with a shooting technique using the terminal concentrations , , , and , using Mathematica's built-in function NDSolve. The blue, magenta, and brown colors correspond to acetone, methanol, and air, respectively. The colored dots shows the solution obtained using the orthogonal collocation technique for user-set values for the number of interior collocation points. As expected, excellent agreement is seen between both numerical methods.