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Nelson Rowell
Phone: 613-993-2377
Fax: 613-952-1394
Email: Nelson.Rowell@nrc-cnrc.gc.ca
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Fixed Point
A cryostat suitable for calibrating capsule platinum resistance thermometers at the triple points of hydrogen, neon, oxygen, and argon in the range 13.8 K to 84 K has been constructed and tested. The design relies on a closed-cycle refrigeration system, obviating the need for liquid helium. High quality triple point measurements of oxygen, neon, and equilibrium deuterium have been obtained.
The freezing point of a pure substance is known to be affected by the presence of impurities. While the freezing point depression or elevation might be assessed with the aid of a chemical analysis and the use of binary phase diagrams, a more direct and accurate determination may be obtained by doping the high purity metal ingots with known amounts of impurities and measuring the resulting effect on the freezing point.
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