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:
“For an instant I see the sky, the different skies, then they turn to faces, agonies, loves, the different loves, happiness too, yes there was that too, unhappily.”
—Samuel Beckett (1906–1989)
“Will TV kill the theater? If the programs I have seen, save for “Kukla, Fran and Ollie,” the ball games and the fights, are any criterion, the theater need not wake up in a cold sweat.”
—Tallulah Bankhead (1903–1968)
“A favorite of outdoor alcoholics, connoisseurs and Fundamentalists, these pills turn water into wine. In 10 minutes the most fetid swamp scum in the forest can become modest red, elusive and light on first taste, yet playful—one might say a trifle impudent—on the afterbite. Saves pack space by eliminating need for bulky corkscrew, decanter and bottles. Store pills on their sides in a cool dark place.”
—Alfred Gingold, U.S. humorist. Items From Our Catalogue, “Wine Pills,” Avon Books (1982)