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Diffusion / Fick’s First Law:- PDF/ PPT


•Definition and concept of diffusion
•Concept of steady state diffusion and the laws involved with it
•Methods and procedures of conducting diffusion
•Applications of diffusion
Explain the concept of diffusion
– Explain steady state and sink condition
– Explain the different laws involved
in the process of
– Explain the different methods and procedures to
conduct the in vitro diffusion experiment
Diffusion is defined as a process of mass transfer of individual molecules of a substance from a region of higher concentration to a region of lower concentration
along a concentration gradient
• Steady state- a system is said to be steady state, if the conditions do not vary with time
• Sink condition – It is a state in which the concentration
in the receptor compartment is maintained at a lower level compared to the concentration in the donor
• In diffusion, molecules(mass) get transported from one
compartment to another over a period of time i.e., rate of
mass transfer(dM/dt).This is expressed as flux
• Flux is equal to the rate of mass transfer across a unit
area of a barrier
• Fick’s second law states that the change in concentration
with time in a particular region is proportional to the
change in the concentration gradient at that point of time


  • Subject:- Physical pharmacutics
  • Course:- B.pharm (pharmacy),
  • Semester:- 3rd sem , sem :- 3