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:
“Change begets change. Nothing propagates so fast. If a man habituated to a narrow circle of cares and pleasures, out of which he seldom travels, step beyond it, though for never so brief a space, his departure from the monotonous scene on which he has been an actor of importance would seem to be the signal for instant confusion.... The mine which Time has slowly dug beneath familiar objects is sprung in an instant; and what was rock before, becomes but sand and dust.”
—Charles Dickens (1812–1870)
“How cold the vacancy
When the phantoms are gone and the shaken realist
First sees reality. The mortal no
Has its emptiness and tragic expirations.”
—Wallace Stevens (1879–1955)
“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)