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:
“How does it become a man to behave toward this American government to-day? I answer, that he cannot without disgrace be associated with it. I cannot for an instant recognize that political organization as my government which is the slave’s government also.”
—Henry David Thoreau (1817–1862)
“Let us not be deceived—we are today in the midst of a cold war.”
—Bernard Baruch (1870–1965)
“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)