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:
“Truly, though our element is time,
We are not suited to the long perspectives
Open at each instant of our lives.”
—Philip Larkin (1922–1986)
“I sat at a table where were rich food and wine in abundance, and obsequious attendance, but sincerity and truth were not; and I went away hungry from the inhospitable board. The hospitality was as cold as the ices. I thought that there was no need of ice to freeze them.”
—Henry David Thoreau (1817–1862)
“You’re nothing but a pack of cards!”
—Lewis Carroll [Charles Lutwidge Dodgson] (1832–1898)