Abstract
Melting points of salts for use as standard temperatures for thermocouples, 400° to 1100°C.—After purification by crystallization from solution, a gram of the salt is placed in a Pt crucible 18 mm by 10 mm in diam., the junction is placed in the axis and 3 to 4 mm from the bottom, and the temperature is raised about 5° per minute. For most pure substances and certain eutectics the heating curve becomes quite flat at the melting point and hence the form of curve obtained is a sensitive test of purity. The couples used were carefully calibrated with standard metals, and gave the following results, accurate to ± 0.5°: potassium dichromate 397.5°; () 627.0°; 770.3°; 800.4°; 884.7°; inversion point 583±1°, melting point 1069.1°; also 1304±5°. Detailed suggestions as to technique are given, also a convenient method of using pure metal strips or wires in calibrating couples.
- Received 12 October 1923
DOI:https://doi.org/10.1103/PhysRev.23.386
©1924 American Physical Society