In CTS the most routinely applied methods for obtaining the pore-size distribution (PSD) of porous solids are physical adsorption of inert gases (e.g. nitrogen, argon, krypton) and high-pressure mercury porosimetry. Helium pycnometry is used for determination of a true skeletal density. Instrumentation for liquid expulsion permporometry has been developed together with the required evaluation software. Thus, distribution of through-pores, which are responsible for mass transfer, can be obtained.