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:
“You held my hand
and were instant to explain
the three rings of danger.”
—Anne Sexton (1928–1974)
“But pale despair and cold tranquillity,
Nature’s vast frame, the web of human things,
Birth and the grave, that are not as they were.”
—Percy Bysshe Shelley (1792–1822)
“The savage soul of game is up at once—
The pack full-opening various, the shrill horn
Resounded from the hills, the neighing steed
Wild for the chase, and the loud hunter’s shout—
O’er a weak, harmless, flying creature, all
Mixed in mad tumult and discordant joy.”
—James Thomson (1700–1748)