تسجيل الدخول

تسجيل

Limitations of Mercury Thermometers

المؤلف:  GEORGE A. HOADLEY

المصدر:  ESSENTIALS OF PHYSICS

الجزء والصفحة:  P-242

2025-11-23

570

The glass bulb of a thermometer may gradually change in volume. There may also be a temporary change after use for high temperatures in which the bulb returns slowly to its original volume. A thermometer, therefore, should be frequently tested to determine what correction is necessary. in reading.

For very low temperatures alcohol is used instead of mercury, which freezes at - 39° C. The ordinary form of mercury thermometer cannot be used for temperatures above 350° С., since its boiling point is 357° C. When the space above the mercury column, however, is filled with nitrogen under pressure, it can be used for temperatures up to 550° C. For still higher temperatures the air thermometer or the electric pyrometer is used.

sure, it can be used for temperatures up to 550° C. For still higher temperatures the air thermometer or the electric pyrometer is used.