NaK (often pronounced as such, rhyming with "sack") is an alloy of sodium and potassium, and particularly one that is liquid at room temperatures. It is a commercially available material in various grades. Alloys with between about 40% and 90% potassium by weight are liquid at room temperatures. General Name, Symbol, Number sodium, Na, 11 Chemical series alkali metals Group, Period, Block 1, 3, s Appearance silvery white Atomic mass 22. ... General Name, Symbol, Number potassium, K, 19 Chemical series alkali metals Group, Period, Block 1, 4, s Appearance silvery white Atomic mass 39. ...

Sodium and Potassium form a eutectic mixture. Proportions of 78% potassium and 22% sodium produce the lowest melting point, this alloy is liquid from −12.6 degrees Celsius to 785 degrees Celsius. A eutectic or eutectic mixture is a mixture of two or more elements which has a lower melting point than any of its constituents. ...

One notable use is as the coolant in experimental fast neutron nuclear reactors. Unlike commercial plants, these are frequently shut down and defuelled. Use of lead or sodium, the other materials used in practical reactors, would require continual heating to maintain the coolant as a liquid. Use of NaK overcomes this. NaK is used in many other heat transfer applications for similar reasons. A coolant, or heat transfer fluid, is a fluid which flows through a device in order to prevent its overheating, transferring the heat produced by the device to other devices that utilize or dissipate it. ... A fast neutron reactor or simply a fast reactor is a category of nuclear reactor in which the fission chain reaction is sustained by fast neutrons. ... General Name, Symbol, Number lead, Pb, 82 Chemical series poor metals Group, Period, Block 14, 6, p Appearance bluish white Atomic mass 207. ... General Name, Symbol, Number sodium, Na, 11 Chemical series alkali metals Group, Period, Block 1, 3, s Appearance silvery white Atomic mass 22. ...

NaK is also used as a catalyst for many reactions, including precursors of ibuprofen. Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID) widely marketed under various trademarks including Act-3, Advil (A portmanteau of Advise and Pill)[citation needed], Brufen, Motrin, Nuprin, and Nurofen. ...

NaK is highly reactive with air or water, and must be handled with special precautions. Quantities as small as one gram can be a fire or explosion risk.

'Nak is also a common term for the city of Allanak found in the southern wastes on the popular game ArmageddonMUD

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