# Fick's Law Of Diffusion

## What is Fick’s law of diffusion?

Fick’s law of diffusion explains about diffusion process (movement of molecules from higher concentration to lower concentration region) to solve diffusion coefficient derived by Adolf Fick in the year 1855.

There are two laws that are interrelated ie; Fick’s first law is used to derive Fick’s second law which is similar to the diffusion equation.

### Fick’s first law

Movement of solute from higher concentration to lower concentration across a concentration gradient.

$J = -D\frac{\mathrm{d} \varphi }{\mathrm{d} x}$

Where,

J: diffusion flux

D: diffusivity

φ: concentration

x: position

### Fick’s second law

Prediction of change in concentration along with time due to diffusion.

$\frac{\partial \varphi }{\partial t} = D \frac{\partial^2 \varphi }{\partial x^2}$

Where,

D: diffusivity

t: time

x: position

Φ: concentration

### Application of Fick’s law

• Biological application:
• $flux = -P(c_{2}-c_{1})$ (from Fick’s first law)

Where,

P: permeability

c2-c1: difference in concentration

• Liquids: Fick’s law is applicable for two miscible liquids when they are brought in contact and diffusion takes place at a macroscopic level.
• Fabrication of semiconductor: Diffusion equations from Fick’s law are used to fabricate integrated circuits.
• Pharmaceutical application
• Applications in food industries.

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