A novel method of determining median pore size and pore size distribut
ions as a function of spatial position inside a porous sample is descr
ibed. Pore sizes have been measured with 1-, 2- and 3-dimensional spat
ial resolution, using NMR cryoporometry in conjunction with magnetic r
esonance imaging techniques. The method is suitable for pore diameters
in the range of 30 Angstrom to over 2000 Angstrom pore diameter, and
is based on the technique of freezing a liquid in the pores and measur
ing the melting temperature by nuclear magnetic resonance. Since the m
elting point is depressed for crystals of small size, the melting poin
t depression gives a measurement of pore size.