Fick’s law of diffusion

Ficks law of diffusion measures the shift of mass through regions. The previous works done in this category by Thomas graham inspired this law. However these works did not suffice to take the form of basic physics laws. Ficks laws states that a mass of molecules moves from the place of high concentration to that of low density. He has advocated a formula for finding the diffusion coefficient.  The law of molecular diffusion states that with more molecules, there is a better movement of the molecules. The randomness in diffusion does not happen when there is lesser number of solute molecules. So, the solute moves easily in the direction of low density. Fick’s law contain this principle of diffusion smoothness. Diffusion happens in all kinds of substances, which even include solids. Before the laws of fick were advocated, the diffusion of solids was considered improbable. But, some of the diffusion processes also don’t happen under these laws. Those components are known as non fickian. This law was formed in the year 1855. So, heat and mass transfer in ficks law of diffusion include an understanding of the heat conduction impact on the process of diffusion. It discusses how does heat impact takes place in a diffusion process. Mass transfer is also discussed when there is mass transfer in a diffusion process. The first law of ficks states that the diffusive flux is proportional to the slope of the concentration field.  This slop is a spatial derivative known as concentration gradient. It describes the magnitude or the flow of the gradient. 

The second law of ficks holds that after some time, the concentration fields change after some time. This happens due to diffusion as the density of the different fields varies. Ficks first law only holds true under certain assumptions and when those assumptions are flouted, the diffusion is non fickian.

Questions:

• What's the formula of ficks law of diffusion?
• What are non fickian diffusions?