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)
“Willows last to relinquish a leaf,
curious, patient, lion-headed, tense
with energy, watching
the serene cold through a curtain
of tarnished strands.”
—Denise Levertov (b. 1923)
“A man was to live in that egg-shell day and night, a mile from the shore.... Think of making your bed thus in the crest of a breaker! To have the waves, like a pack of hungry wolves, eying you always, night and day, and from time to time making a spring at you, almost sure to have you at last.”
—Henry David Thoreau (1817–1862)