Fick's second law

[member 392791]

Hello,

I read on wikipedia that the second law represents how concentration changes with time, but I was wondering how taking the partial derivative with respect to x of the first law will give change in concentration with time?

 

[nasu]

See here, for example:
http://en.wikipedia.org/wiki/Fick's_laws_of_diffusion

It's not that you get the second law just by taking the derivative of the first law. Conservation of mass is used as well.