Mercury thermometer usage limits: For low-temperature measurement, what are the approximate freezing point and boiling point of mercury in °C that bound the useful range of a mercury-in-glass thermometer?

Introduction / Context:
Mercury-in-glass thermometers are traditional contact thermometers. Their usable range is fundamentally limited by the physical properties of mercury: freezing near −38.8 °C and boiling near 356.7 °C at 1 atm. Knowledge of these limits prevents misuse and breakage.

Given Data / Assumptions:

• Standard atmospheric pressure conditions.
• Rounded choices approximating physical constants.
• Typical laboratory thermometers without special pressurization.

Concept / Approach:
Because mercury freezes around −39 °C, measurements below this temperature require alternative fills (e.g., alcohol, toluene) or platinum resistance thermometers. Boiling near 357 °C limits upper range unless the bulb is pressurized; most common mercury thermometers therefore top out around 350 °C.

Step-by-Step Solution:

Verification / Alternative check:
Materials data and instrument catalogs specify −39 °C and ≈ 357 °C; answer choice (−39, 350) reflects practical range limits.

Why Other Options Are Wrong:

Common Pitfalls:
Using mercury thermometers at sub-zero temperatures where the column may fracture or separate; also environmental restrictions on mercury require safer alternatives.

Final Answer:
-39 and 350