When ice water is not cool enough for use as a bath, salt and ice may be used. For even lower temperatures, dry ice may be used with an organic liquid. An ideal cooling liquid for use with dry ice should have the following characteristics:
Cryogenic coolants should always be used with caution. Cryogenic liquids must be handled in properly vented containers. Be aware that very low temperature coolants, such as liquid nitrogen, may condense oxygen and cause an explosion with combustible materials. Use gloves and face shields, slowly immerse the object to be cooled to avoid too vigorous boiling and overflow of the coolant. Glass Dewar flasks should be of borosilcate glass and protected by covering with cloth-backed friction or duct tape or encased in metal sheath to contain flying pieces in the event of implosion.
Avoid pouring cold liquid onto the edge of a glass Dewar flask when filling because the flask may break and implode, For the same reason do not pour a cryogenic liquid out of a glass Dewar flask; use mild air pressure or a siphon. Metal or plastic Dewar type flasks are preferable and eliminate this problem. Never use a household Thermos bottle in place of a Dewar flask
Do not lower your head into a dry ice chest. Because no oxygen is present, suffocation can result. Do not handle the dry ice with bare hands; if the skin is even slightly moist, severe burns can result. Use dry leather or suitable cryo-gloves. When chipping dry ice, wear goggles.
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