porvolume

Porvolume, commonly referred to as pore volume, is the total volume of void spaces inside a solid that can be occupied by a fluid. It is usually expressed in units such as cubic centimeters per gram (cm^3/g) or as a dimensionless fraction relative to the bulk volume. Porvolume is related to porosity by the equation φ = V_p / V_t, where V_t is the total (bulk) volume of the material. Thus porvolume represents the absolute space available in the material’s pores, while porosity is the fraction of that space relative to the whole.

A key distinction is between the total pore volume and the portion accessible to a given penetrant. Accessibility depends on pore size, connectivity, and the chemical nature of the pore surfaces. Some pores may be inaccessible to certain fluids or molecules, especially if the pore throat is too small.

Measurement and estimation methods include gas adsorption (for example nitrogen at 77 K) to determine surface area and pore volume via adsorption isotherms, mercury intrusion porosimetry to map pore size distribution and cumulative pore volume, and gravimetric or volumetric methods in which a probe liquid saturates the pores. When using a liquid to estimate V_p, the sample is saturated with a known-density liquid and the mass uptake is used to compute the pore volume, with corrections for density and bulk material.

Applications span catalysis, filtration, energy storage, and soil science. Materials such as activated carbons and mesoporous silicas are often characterized by their porvolume to assess adsorption capacity and transport properties. The term is sometimes shortened to “porvolume,” though many sources prefer “pore volume.”