Abstract: The invention relates to a method of determining at least one quantity relative to the adsorption of at least one adsorbable gas in a sample of a porous medium, wherein the following steps are carried out: (i) determining a Darcy velocity by injecting an inert gas for a given gradient and by measuring the inert gas flow rate downstream from the sample, (ii) determining an adsorbable gas breakthrough velocity by injecting the adsorbable gas for the same gradient and by measuring the adsorbable gas quantity downstream from the sample as a function of time, and (iii) determining a kinematic porosity using the ratio of the Darcy velocity to the adsorbable gas breakthrough velocity.