The Unidirectional Diffusion of a Gas A though a second stagnant Gas B (`N_b` = 0) is represented by `N_A` which is the diffusive flux of component i through area A in z direction.
Diffusive equilibrium is when the concentrations of all materials are equally distributed. This equation uses a value for the Universal Gas Constant, R, with units of (liter*atm / mol*K). Molecular Diffusion is quantified as diffusive flux measured in units of mole/(time x area). This equation utilizes different partial pressure samples. `lm` represents the 'log mean' of the samples taken.