Thermometer, Laboratory

Quick Answer: The Thermometer, Laboratory is a general-purpose liquid-in-glass thermometer for measuring the temperature of liquids and gases in school, college and routine laboratory work. A laboratory thermometer is the default instrument for water baths, heating and cooling experiments and boiling-point measurements.

Immersion: The Detail Most Readings Get Wrong

Liquid-in-glass thermometers are graduated for a particular immersion. A total-immersion thermometer is meant to be immersed up to the level of the liquid column, while a partial-immersion thermometer has a line etched around the stem and only the part below that line should be in the medium. If a total-immersion thermometer is read with much of its column sticking out into cooler air, the exposed liquid contracts and the reading comes out low, an error that grows the hotter the medium is.

Reading technique matters as much. Keep the eye level with the top of the column to avoid parallax, read a mercury thread at the top of its convex surface and a spirit thread at the bottom of its concave one, and wait until the column stops moving. In heating experiments, stir the liquid and keep the bulb clear of the container’s base, which is hotter than the liquid above it.

The title does not state the range, filling or immersion type of this thermometer, and those should be matched to the work. For finer readings over a narrow span see the precision thermometer; for the enclosed-scale design, the enclosing type thermometer.

Specifications

Applications

• Heating and cooling curves of water and wax in school physics and chemistry
• Measuring the boiling point of water and seeing how dissolved salt raises it
• Holding water baths at set temperatures during enzyme and germination practicals
• Recording temperature change in neutralisation and dissolving experiments

Care & Handling

• Clamp the thermometer or rest it in a holder; never use it as a stirring rod.
• Heat and cool gradually; moving it straight from hot liquid into cold water can crack the bulb.
• Do not exceed the top of the scale, where the capillary can burst.
• Store it flat in a padded case or upright in a rack, bulb down.

Why Choose LabEquip

Schools, colleges and quality-control labs order general laboratory thermometers in the largest numbers, since every practical bench needs one. LabEquip lists them in General Lab Products; send range and quantity details through the contact page.

Frequently Asked Questions

What is the difference between total and partial immersion?

A total-immersion thermometer is calibrated with the bulb and the whole liquid column in the medium. A partial-immersion one has a line on the stem and is calibrated with only the part below that line immersed. Using the wrong depth introduces an error.

Should I read the top or the bottom of the liquid?

Read at the top of a mercury thread’s curved surface and at the bottom of a spirit thread’s curved surface, with your eye level with the thread.

Why does my thermometer read above 100 °C in boiling salt water?

Dissolved salt raises the boiling point of water, so the solution boils above the temperature of pure water. This is an expected result, not an error.

Can it be put in a flame?

No. The thermometer should only be in the liquid or gas being measured. A direct flame heats the glass unevenly and can take the liquid beyond the scale, breaking it.

How can I check it?

Place it in a slurry of crushed ice and distilled water; it should read close to 0 °C. The boiling point of pure water is also a check, but it varies with atmospheric pressure and altitude.

What is the difference between mercury and spirit fillings?

Mercury gives a fine, opaque thread and covers higher temperatures; coloured spirit is far less toxic and reads well below the freezing point of mercury, but cannot reach high temperatures. Many schools now choose spirit for safety.

Last Updated: September 2026