LABORATORY THERMOMETER: CHARACTERISTICS, TYPES, HISTORY - CHEMISTRY - 2024

The laboratory thermometer is an instrument used to measure the exact temperature of substances. By being able to measure the temperature through a thermometer, it can be controlled. This instrument is manufactured to calculate both low and high temperatures.

There are materials that respond to different temperatures, such as some metals, for example, mercury (liquid substance). For this reason, the thermometer is designed with a tube, generally made of glass, that has mercury inside.

On the outside, it has written the temperatures that it can measure. In addition, a metal point protrudes at one of the ends that will be the one that will come into contact with what is to be measured.

When the metal tip comes into contact with a substance, the mercury begins to expand when it senses a different temperature. This makes it rise up the length of the tube, passing the numerical scale until it stops at that figure that will indicate the temperature at which the substance is found.

This is the description of a modern laboratory thermometer. Formerly, the tube had an opening at one end, which was submerged in the liquid (water with alcohol) to be measured.

Inside the tube was a sphere that rose depending on the temperature of the liquid.

History of the laboratory thermometer

The laboratory thermometer was born from the aspiration to measure temperatures in general. The first idea of ​​an instrument to measure temperature is attributed to Galileo Galilei, who in 1593 created a way to measure the change of temperature in water. This is what is currently known as a thermoscope.

In 1612, the Italian Santorio Santorio, added a numerical scale to the idea of ​​Galileo Galilei. This can be considered as a first approach to the clinical thermometer.

However, Ferdinand II, Duke of Tuscany, modified Galilei and Santorio's design in 1654. His modifications consisted of closing both ends of the tube and changing the water for alcohol to determine the temperature. Despite its reforms, this was not a fully functional thermometer either.

The person who transformed the thermometer to the modern model was Daniel Gabriel Fahrenheit. In 1714, this man decided to change the liquid used for mercury. In this way, it became possible to measure lower and higher temperatures.

Measurement scales

There are different types of scales on which a thermometer can mark the temperature, whether it is laboratory or not. The scales are as follows:

- Celsius or centigrade (ºC), created by Anders Celsius, a Swedish astronomer. In 1742, he proposed a scale from 0ºC to 100ºC, with 0 representing the lowest temperature and 100 the highest.

- Fahrenheit (ºF), named by its creator, Daniel Fahrenheit, in 1724. This scale is 180 divisions, with 32 ºF being the coldest point and 212 ºF being the hottest point. Fahrenheit created this scale using human body heat, measured at 98.6ºF, as a reference.

- Kelvin (ºK), like the previous ones, this one also bears the name of its inventor, Lord Kelvin (William Thomson). This scale was invented in 1848 and was based on the Celsius scale.

Maintenance

It can be thought that a thermometer does not need any type of maintenance, since it works with the change of temperature.

However, like many other measuring instruments, the thermometer must be calibrated to avoid errors in its operation.

There are some thermometers that are used to calibrate. Sometimes calibration can be done at home, but if this is not possible, it is necessary to consult an expert.

Types

For the most part, thermometers work the same way. However, even when their objective is the same (that is, to measure the temperature to be able to control it) there are different types of laboratory thermometers and some of them are the following:

Liquid thermometer in glass

This type is the most common. It is a sealed glass tube that contains mercury or red alcohol inside it, since the danger posed by contact with mercury has been studied.

These two types of liquids react with the change in temperature, either by contracting if it is low or expanding if it is high.

Usually this type of thermometer is represented on a Celsius scale, but it can also be found on the Fahrenheit scale.

Bimetallic foil thermometer

The bimetallic foil thermometer is formed, as its name indicates, with two metallic foils that are attached to each other, but that react differently. These sheets bend when they come into contact with a change in temperature.

This movement is perceived by a spiral, which is translated through a needle the level of temperature that it is measuring.

Digital thermometer

Digital thermometers are made with a microchip that receives the information that electronic circuits capture about temperature. The microchip receives and analyzes the information and then displays the numerical results on the screen.

In addition, an advantageous feature of this model is that it does not have any type of component that can be harmful to life.

These thermometers, being part of technological advances, can do more than just measure temperature. The more its functions, the higher its cost.

Infrared thermometer

The infrared thermometer, also known as an infrared pyrometer or non-contact thermometer, differs from other types of thermometers by measuring thermal radiation and not temperature as such.

Thanks to its built-in infrared technology, it is capable of measuring the temperature of what you want, without the need to touch it or be close to it.

Therefore, this thermometer is functional to measure those substances or objects with which it is not advisable to come into contact.

Resistance thermometer

The temperature with this type of thermometer is measured through an electrical resistance and a platinum wire or another kind of pure material incorporated, which respond to changes in temperature.

It is considered that although the levels that it marks are exact, it is a bit slow.

References

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