An instant cold pack is a device that consists of two bags, one containing water, which is inside a second bag containing ammonium nitrate. When the inner bag is broken by squeezing the package, the ammonium nitrate is allowed to dissolve in the water in an endothermic reaction. This reaction absorbs heat from the surroundings, quickly lowering the pack's temperature.
Instant cold packs are a convenient direct replacement for crushed ice used as first aid on sport injuries. It is also important not to refrigerate before activation. This may result in frostbite if used for prolonged periods of time.
For safety reasons, instant cold packs have recently been developed without ammonium nitrate.
Famous quotes containing the words instant, cold and/or pack:
“Power ceases in the instant of repose; it resides in the moment of transition from a past to a new state, in the shooting of the gulf, in the darting to an aim.”
—Ralph Waldo Emerson (1803–1882)
“Our American professors like their literature clear and cold and pure and very dead.”
—Sinclair Lewis (1885–1951)
“You’re nothing but a pack of cards!”
—Lewis Carroll [Charles Lutwidge Dodgson] (1832–1898)