Creating Liquid Nitrogen Continued                          Absorb_pic                                                      Membrane_pic Absorption Processes (for smaller applications and provides less pure nitrogen samples)  This method takes advantage of chemical properties of the element and compresses air through absorbent materials which absorb different elements in the air, this will leave a sample that is of a majority composed of nitrogen.  According to http://uigi.com/noncryo.html the material often used for absorbing oxygen and leaving nitrogen is an activated carbon molecular sieve.   Membrane Diffusion (for deriving small quantities of nitrogen at a lower purity)             This method takes advantage of the fact that different materials diffuse through polymer lined tubes at different rates.  Specifically nitrogen and argon diffuse at a slower rate than oxygen and CO2.