Vacuum Flask
ALTERNATIVE NAME/S: Thermos bottle; Dewar flask
DETAILS/DESCRIPTION:
In 1892 Scottish physicist James Dewar* invented a Vacuum flask later generally known as a Dewar flask. Since his principal interest at the time was low-temperarure work, Dewar wanted a way to keep gases in frozen, liquid form. His flask consisted of two silvered glass bottles, one inside the other and separated only by a very small gap. The bottles were sealed together at the necks after all the air had been drawn out from the space between them, leaving a vacuum.
Glass is a very poor conductor of heat, so liquids inside the flask soon settled into thermal equilibrium, with the inner bottle wall losing only a fraction of their heat to the glass. As the vacuum transmits heat only by radiation, the silvered surfaces of both bottles kept this to a minimum.
The silvered glass and vacuum cut down on radiation and convection, so the temperature of the flask contents stayed within a fraction of a degree.
In 1904 the name ‘Thermos’ was coined by a German company.
ONELINER: The vacuum flask
OTHER CONNECTIONS: None
BIBLIOGRAPHY:
Encyclopedia Britannica
Multimedia:
Patented: History of Inventions Thermos Flask: A Hot and Cold History Spotify ; [video $]