Liquid Nitrogen

This truck refills our liquid nitrogen tanks.  Liquid nitrogen is important for storing delicate samples like chemically competent cells and cell extract.  The most damaging part of freezing samples for storage is the formation of ice crystals.  This growth occurs in the intermediate zone of ~-15C to -60C.  Flash freezing samples helps them quickly pass through the intermediate zone.  It also helps the water form amorphous ice, vitrified ice, instead of crystal ice.  Once at -80C the samples are relatively stable.  Ideally, samples could be stored at -130C because at this temperature no liquid water remains, and at -196, liquid nitrogen temperatures, no thermally driven reactions can occur.  (Mazur 1984)