Introduction:
Permeability is a measure of how easily a fluid can flow through a porous medium. It is an important property in various engineering applications such as groundwater flow, soil mechanics, and petroleum engineering. The physical properties of the permeant (the fluid flowing through the medium) play a significant role in determining the permeability of the medium.

Explanation:
The physical properties of the permeant that influence permeability are viscosity and unit weight. Let's discuss each of these properties in detail:

Viscosity:
Viscosity is a measure of a fluid's resistance to flow. It determines how easily the fluid can deform and flow through the pores of the medium. The viscosity of a permeant affects the rate of flow through the medium. A more viscous fluid, such as thick oil, will have a higher resistance to flow and will flow more slowly through the pores. On the other hand, a less viscous fluid, such as water, will flow more easily through the pores. Therefore, the viscosity of the permeant directly influences the permeability of the medium.

Unit Weight:
Unit weight is the weight per unit volume of a substance. It is a measure of the density of the fluid. The unit weight of the permeant affects the pressure exerted on the medium and, consequently, the flow of the fluid. A fluid with a higher unit weight will exert more pressure on the medium and will tend to flow more easily through the pores. On the other hand, a fluid with a lower unit weight will exert less pressure and will flow more slowly through the pores. Therefore, the unit weight of the permeant also plays a significant role in determining the permeability of the medium.

Conclusion:
In conclusion, the physical properties of the permeant that influence permeability are viscosity and unit weight. Viscosity determines the resistance to flow, while unit weight determines the pressure exerted on the medium. Both of these properties directly affect the flow of the fluid through the pores of the medium and, therefore, the permeability. It is important to consider these properties when analyzing the permeability of a porous medium in various engineering applications.