Dewar flask

n.
An insulated container used especially to store liquefied gases, having a double wall with a vacuum between the walls and silvered surfaces facing the vacuum.

[After Sir James DEWAR.]

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A vessel having double walls, the space between being evacuated and the surfaces facing the vacuum being heat reflective. It was invented in 1892 by James Dewar as a container for liquid oxygen.

Dewar's original flasks were made of glass with a coating of mirror silver; this type is still used in the laboratory. But for shipment and storage of liquid gases, metal vacuum vessels are used (see illustration). Thermos Bottle is a trademark for a Dewar vessel for hot and cold foods.

A typical Dewar container.

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or Dewar

a double-walled vessel or flask, usually of silvered glass but sometimes of metal, in which the space between the walls is evacuated to prevent conduction and convection of heat between the inner and outer walls. It is used to maintain the contents at temperatures either higher or lower than that of the environment. [After its inventor Sir James Dewar (1842 — 1923), British chemist and physicist.]

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An insulated container for the storage of cryogenic liquids such as liquid nitrogen.