You wish to identify the nominal diameter of the pores through an alumina filtration membrane that has very uniform, cylindrical pore diameters. You lost the packaging label and you would crack the filter trying to image it. It is brittle. You can mechanically support it in a device. You can apply a gas on the high pressure side and a vacuum (~1kPa) on the low pressure side. You know the membrane area and can measure the mass flowrate going through the filter. You can vary the pressure on the high pressure side and you can change the gas among common gases. How do you expect the mass flowrate to vary with pressure, gas used, and possible pore size of the filter? How would you assess the pore size in the shortest amount of time and effort?