Vacuum flask

A vacuum flask (also known as a Dewar flask, Dewar bottle or Thermos) is an insulating storage vessel that greatly lengthens the time over which its contents remain hotter or cooler than the flask's surroundings. Invented by Sir James Dewar in 1892, the vacuum flask consists of two flasks, placed one within the other and joined at the neck. The gap between the two flasks is partially evacuated of air, creating a near-vacuum which significantly reduces heat transfer by conduction or convection.

Vacuum flasks are used domestically to keep beverages hot or cold for extended periods of time and for many purposes in industry.

History

The vacuum flask was designed and invented by Scottish scientist Sir James Dewar in 1892 as a result of his research in the field of cryogenics and is sometimes called a Dewar flask in his honour. While performing experiments in determining the specific heat of the element of palladium, Dewar formed a brass chamber that he enclosed in another chamber to keep the palladium at its desired temperature. He evacuated the air between the two chambers creating a partial vacuum to keep the temperature of the contents stable. Through the need for this insulated container, James Dewar created the vacuum flask which became a significant tool for chemical experiments but also became a common household item. The flask was later developed using new materials such as glass and aluminum; however, Dewar refused to patent his invention.