Describing a Filter Medium

摘要

Some time ago a writer described his filter medium as a really big thing. But the only addition to that description was, "It is produced according to Patent Number so and so." He said nothing about the material(s) of construction, thickness, porosity, permeability, or pore size. How could he sell his product without revealing those "secrets"? In contrast, Millipore, in 1970, offering the new ultra-filtration membranes, reported materials of construction, thickness, porosity, along with data from which one may deduce the permeability of air and water, from which one may deduce the laminar-flow-averaged pore diameters.