A Dewar flask is a vessel designed to provide very good thermal insulation. For instance, when filled with a hot liquid, the vessel will not allow the heat to easily escape, and the liquid will stay hot for far longer than in a typical container. The Dewar flask was named after its inventor Scottish physicist Sir James Dewar (1842–1923). This page refers to thermal insulation. ... A red-hot iron rod cooling after being worked by a blacksmith. ... Royal motto: Nemo me impune lacessit (English: No one provokes me with impunity) Scotlands location within the UK Languages English, Gaelic, Scots Capital Edinburgh Largest city Glasgow First Minister Jack McConnell Area - Total - % water Ranked 2nd UK 78,782 km² 1. ... A physicist is a scientist trained in physics. ... James Dewar (1842–1923) Sir James Dewar (September 20, 1842 – March 27, 1923) was a Scottish chemist and physicist. ... 1842 was a common year starting on Saturday (see link for calendar). ... 1923 (MCMXXIII) was a common year starting on Monday (link will take you to calendar). ...

In form, a Dewar flask is a glass or metal bottle, with a double-layer construction; in fact, it can be considered to be two thin-walled bottles nested one inside the other, and sealed together at the neck. The narrow space between is evacuated almost entirely of air; the near vacuum prevents conduction and convection of heat. This article refers to the material. ... Layers of Atmosphere (NOAA) Earths atmosphere is a layer of gases surrounding the planet Earth and retained by the Earths gravity. ... For other uses, see vacuum cleaner and Vacuum (musical group). ... Heat flow along perfectly insulated wire Heat conduction is the transmission of heat across matter. ... Convection is the transfer of heat by currents within a fluid. ...

The inner surfaces of the outer bottle, and the outer surface of the inner bottle, have a metallic or similar reflective coating to prevent heat from being transmitted via radiation. Dewar himself used silver for this purpose. This is so effective that what little heat transport does occur is almost entirely via the neck and stopper; insulating materials such as cork are often used for the stopper. Thermal radiation, or radiant heat, is electromagnetic radiation from an object that is simply caused by its temperature. ... General Name, Symbol, Number silver, Ag, 47 Chemical series transition metals Group, Period, Block 11, 5, d Appearance lustrous white metal Atomic mass 107. ... A cork stopper for a wine bottle A Champagne cork Cork material is a subset of generic cork tissue, harvested for commercial use primarily from the Cork Oak tree, Quercus suber, with Portugal producing most cork worldwide. ...

A very common use of the Dewar flask in laboratories is the storage of liquid nitrogen; in this case, the leakage of heat into the extremely cold interior of the bottle results in a slow "boiling-off" of the liquid (a pressure relief valve is provided to prevent pressure from building up). The excellent insulation of the Dewar flask results in a very slow "boil" and thus the nitrogen lasts a long time without the need for expensive refrigeration equipment. General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless Atomic mass 14. ... Relief Valve A relief valve opens to release excess pressure when the pressure is too high to protect the vessel or other equipment from overpressurization. ... Pressure (symbol: p) is the force per unit area acting on a surface in a direction perpendicular to that surface. ... Refrigeration (from the Latin frigus, frost) is generally the cooling of a body by the transfer of a portion of its heat away from it. ...

A "Thermos bottle" (trademarked), or vacuum flask (generic) used to keep coffee or other beverages hot, is usually based on the design of a Dewar flask; since glass dewar flasks are fragile and somewhat expensive to fabricate, other constructions based on plastic or insulated metal are also popular. A trademark (Commonwealth English: trade mark) is a distinctive sign of some kind which is used by a business to uniquely identify itself and its products and services to consumers, and to distinguish the business and its products or services from those of other businesses. ... Lunchbox and vacuum bottle owned by Harry S. Truman A vacuum flask or Thermos flask is a bottle that reduces heat transfer from the inside to the outside and conversely to a minimum, and therefore keeps warm drinks warm and refrigerated drinks cold. ... Coffee in beverage form. ... Plastic is a term that covers a range of synthetic or semisynthetic polymerization products. ...

See also

• Cryogenics
• Dewar tube

Cryogenics is a branch of physics (or engineering) that studies very low temperatures or the production thereof. ... Dewar tubes are constructed like Dewar flasks, but unsilvered and open at both ends, to allow a heat transfer fluid to flow through and absorb sunlight. ...

Patents

• Burger, R., U.S. Patent 872795, "Double walled vessel with a space for a vacuum between the walls", December 3, 1907.