8 junio, 2024

Laboratory thermometer: characteristics, what it is for, use, examples

He laboratory thermometer It is a measuring instrument with which the temperature, either high or low, of different substances, mainly liquid or gaseous, is determined. Its accuracy and precision are characterized by being superior to those of other thermometers.

The word ‘thermometer’ includes ‘thermo’ of heat and ‘meter’ of measuring, of determining. Therefore, the thermometer is a device with which it is possible to determine the magnitude of the vibratory energy that the molecules of a substance present. This energy is manifested as heat and its intensity is determined by a specific value of temperature.

The thermometer is a very frequently used instrument in research laboratories, routine, clinical centers, the pharmaceutical industry, food, among other areas.

The most commonly used is that of liquid in glass (upper image), which has a temperature sensor or thermometric substance, which expands or contracts with the increase or decrease in temperature. An example of this is alcohol dyed red or mercury, among others depending on the type of thermometer.

These types of thermometers are not very affordable because of the cost. For its use it has to be in contact with the substance to be measured, since it does not maintain the temperature reached like clinical thermometers. They are not suitable for measuring body temperatures.


Laboratory Thermometer Features

The most widely used laboratory thermometer is the liquid-in-glass thermometer. There are several characteristics that it possesses and the following stand out:


The most commonly used laboratory thermometer is a glass tube about 30 cm long. It has a triangular or round shape, and contains the thermometric scale on its external surface. Inside it contains the stem or capillary through which the mercury or alcohol moves.

These thermometric substances are stored at one end called the bulb. The thermometer has one end opposite the bulb, which ends in a hollow circular ring. By means of this ring, the thermometer can be held to keep it immersed during the measurement process or test.


The laboratory thermometer is characterized by having a high sensitivity. A small increase in heat will cause the liquid contained in the bulb to expand, producing a proportional change in the length of the wire up the capillary of the thermometer.

fine bulb

The function of the bulb is to contain the thermometric substance. It is the part that must be in contact with the solution to be measured. Laboratory thermometers are characterized by having a thin bulb, which makes them more sensitive to changes in temperature.


With the laboratory thermometer, temperatures that oscillate within a wide range can be determined: from -10°C to 200 or even 357°C approximately. The range is determined by the freezing and boiling point of the thermometric substance.

temperature scale

The laboratory thermometer has a temperature scale or thermometric scale expressed in Fahrenheit (°F), in Celsius (°C), which is the most widely used scale today, or in some with the Kelvin (K) scale.

without valve

The laboratory thermometer is characterized by the fact that it does not have a valve or connection pleats between the bulb and the stem. This valve causes the mercury or alcohol to go down or slowly return to the bulb.

Without this valve the thermometric liquid sinks rapidly, providing an unreliable reading when it is withdrawn from the substance of measurement. For this reason, the laboratory thermometer has to stay in contact with the substance to correctly measure the temperature.


They are resistant to temperature fluctuations, since in their preparation they are subjected to processes such as thermal tempering.


measure temperature

The fundamental use of the laboratory thermometer is to measure the temperature with high precision of different substances, whether they are in a liquid, solid or gaseous state.

There are thermometers that have alcohol dyed red inside in order to facilitate the observation of the mark that reaches the temperature. As mercury or alcohol traverses the numerical scale in proportion to the heat it receives, the temperature can be accurately determined.

For these purposes, thermometers are used in industry, in quality control laboratories, in experimental laboratories or in diagnostic routines.

Measure physical properties

Laboratory thermometers are used to make determinations of physical properties of substances such as freezing point and boiling point, among others.

Control chemical processes

The laboratory thermometer is also used in order to control and regulate the development of different processes or chemical reactions at a certain temperature, such as enzymatic determinations, for example.

It is useful to monitor experiments, to measure the temperature of different metals, of test materials, among other scientific procedures.

How is the laboratory thermometer used?

To measure the temperature, the laboratory thermometer must be placed vertically. It should not be tilted and may be partially immersed. It is recommended to immerse the thermometer at half the height of the solution to which you want to determine the temperature.

Avoid touching the walls, bottom or base of the container with the thermometer, especially when the substances to be measured are being boiled. This is because the temperature of the walls or the bottom in general are usually higher than that of the contained material.

The bulb must be kept inside the substance or material while the temperature is required to be measured. It should not be removed to carry out the reading process because the temperature would fluctuate rapidly, reflecting that of the surrounding environment.

The thermometer requires to be very clean before use. Maintenance and care is essential, like all laboratory equipment, and it must be calibrated to avoid errors in its use.

Examples of use

Some examples of its use are listed to finish:

-The laboratory thermometer is used to measure the temperature in different processes of monitoring experiments, material tests, among others.

-It is an instrument of mandatory presence in the different research, quality control, and sample processing laboratories, among many others.

-It is used to determine the boiling point of substances, the freezing point, or to verify the temperature of solvents.

-It is required to measure the maximum and minimum temperatures of certain environments or physical spaces in which it is important to maintain sterile working conditions.

-The calibrated laboratory thermometer is used in the verification or calibration processes of another thermometer.

There are other types of more specialized thermometers, such as radiation, which is used to measure the temperature of those substances with which it is convenient not to come into contact.

The nature of the investigation will determine what type of laboratory thermometer should be used, since there are digital and infrared thermometers, among others.


Lifepersona.com. (2020). Laboratory Thermometer: Features, Types, History. Recovered from: lifepersona.com
Wikipedia. (2020). Thermometer. Retrieved from: simple.wikipedia.org
Byjus. (nd). Thermometer: Clinical & Laboratory Thermometer. Recovered from: byjus.com
Mini Physics (2015). Laboratory thermometer. Retrieved from: miniphysics.com
Labcompare. (nd). Laboratory Thermometer. Retrieved from: labcompare.com
BrownG. (2019). Difference between Laboratory Thermometer and Clinical Thermometer. Retrieved from: differencebetween.net

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