kvicksilverintrusion

kvicksilverintrusion is the experimental technique of mercury intrusion porosimetry used to determine pore size distribution and porosity in porous solids. The term blends kvicksilver, the Swedish word for mercury, with intrusion, reflecting its historic use in Nordic scientific literature. The method relies on mercury’s non-wetting behavior with most solids; by applying external pressure, mercury is forced into progressively larger pores.

The relationship between applied pressure P and pore radius r is described by the Washburn equation: r = -2 γ cos θ / P, where γ is the surface tension of mercury and θ is the contact angle between mercury and the solid. Typical values are γ ≈ 0.485 N/m and θ around 140°, yielding pore radii that can be inferred from measured pressure. Pressure ranges commonly extend from about 0.01 to 400 MPa, enabling analysis of pore sizes from nanometers to several hundred micrometers.

Applications include characterization of soils, clays, cement paste, fired ceramics, activated carbons, and catalysts. The method provides cumulative and differential pore size distributions, total porosity, and insights into pore connectivity. It is destructive to the sample and uses toxic mercury, necessitating proper containment, ventilation, and waste handling.

Limitations include variability in wetting behavior, effects of sample preparation, potential for inaccessible pores due to trapped gas, and the possibility that high-pressure intrusion alters fragile pore structures. Mercury porosimetry is often used in conjunction with other techniques, such as gas adsorption (BET) and imaging methods, to provide a comprehensive view of porosity.