The Collaborative International Dictionary of English v.0.48:

Atmolysis \At*mol"y*sis\, n. [Gr. ? vapor + ? a loosing, ? to
   loose.] (Chem.)
   The act or process of separating mingled gases of unequal
   diffusibility by transmission through porous substances. See
   also gaseous diffusion.
   [1913 Webster]