Abstract: The main problem in liquid porosimetry) which prevents to see the pore sizes smaller than 2 microns in diameter, is direct gas diffusion flow through a micro-porous membrane. This diffusion causes bubbles formation on the bottom side of the membrane and that spoils extrusion (intrusion) data, as one cannot distinguish the volume of extrusion (intrusion) liquid from the volume of formatted bubbles. The suggested method cures the problem by creating the liquid flow below the membrane. The flow washes out all of the small bubbles preventing them to grow. That allows using the membrane at higher differential pressures, up to minimum bubble point of the membrane.

Abstract: A porosimeter includes a pressurizable sample chamber with a membrane located directly below the sample. The membrane pores have a smaller size than any of the sample pores of interest. A fluid reservoir is located below the membrane such that the reservoir and the membrane form a seal. In operation, as fluid enters the fluid reservoir through the membrane or a reservoir inlet, fluid already in the fluid reservoir is displaced through a reservoir exit. An inlet in a fluid displacement reservoir receives the fluid displaced from the fluid reservoir. A recirculation line receives fluid from the exit of the fluid displacement reservoir and circulates the fluid into the inlet of the fluid reservoir. In a preferred embodiment, a pump recirculates the fluid through the recirculation line. Fluid returned to the reservoir circulates over the bottom of the membrane, and sweeps air bubbles out of the reservoir.