Derivation of Flux Relationships in One-Dimension

Consider a tube filled with an isobaric binary gas mixture of components A and B. When component A moves it exerts a force on B. This frictional force, can be described as  

JTab = (proportionality constant) (concentration of A) (concentration of B) (relative velocity of A to B) 

Multiply Equation (C.1.2) by C (total concentration) and rearrange to give  

Equation (C. 1.5) is Fick s First Law. To see this, rearrange Equation (C. 1.5) as shown 

Further arrangements of Equation (C.1.6) can be made as shown below  

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