On this day

On 27th March 1923, James Dewar, the Scottish chemist and physicist died.  He is probably best known for his invention of the Dewar Flask which he used in conjunction with extensive research into the liquefaction of gases. He was also particularly interested in atomic and molecular spectroscopy, working in these fields for more than 25 years.

 (20 September 1842 – 27 March 1923)

By 1891 James Dewar had designed and built machinery which yielded liquid oxygen in industrial quantities. Around 1892 the idea occurred to him of using vacuum-jacketed vessels for the storage of liquid gases – the Dewar flask (otherwise known as a Thermos or vacuum flask) – the invention for which he became most famous. The vacuum flask was so efficient at keeping heat out that it was found possible to preserve the liquids for comparatively long periods, making examination of their optical properties possible. Dewar did not profit from the widespread adoption of his vacuum flask – he lost a court case against Thermos concerning the patent for his invention. While Dewar was recognised as the inventor, because he did not patent his invention there was no way to stop Thermos from using the design.

The vacuum flask consists of two flasks, placed one inside the other and joined at the neck. The gap between the two flasks is partially evacuated of air, creating a near-vacuum which prevents 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.

Dewar flasks

Various sizes of Dewar flask are available and are commonly used in Cryogenics for the storage of tissue samples for example.  See also, the safe use of liquid nitrogen by clicking here.

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Posted on March 27, 2015, in Useful Information. Bookmark the permalink. Leave a comment.

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