The Invention of Mercury Thermometer

Invention of Thermometer

Who Invented? : Dante Gabriel Fahrenheit

When Invented? : Year 1714

In which country? : Poland

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Today every store and shops welcomes us with a thermometer because of this COVID-19 situation. Nowadays it becomes precautions for every person to check up their body temperature here’s the origin story of the tool that’s had us on edge since the crisis began.

Since the 400BC, temperature of human body considered as diagnostic sign since the earliest days of clinical medicine. At that time human hand used for detecting higher temperature of human body called fever, but instruments to measure this temperature were not developed until the sixteenth and seventeenth centuries.

1593 Thermoscope

The earliest thermal instrument was developed in sixteenth century. In 1593, Italian inventor, Galileo Galilei first ever tried to make an instrument to measure the heat or temperature. He was the first inventor of rudimentary thermoscope. It contains a glass tube filled with water and glass bulbs of varying masses, each with a temperature marking. The glass bulbs sink as the temperature of the water rise because increase in the water temperature lead to change in lightness of water. Here the lowest bulb indicates what temperature it was.  The invention of Galileo Galilei was called  Gelileo thermometer. However the invention was not strictly called the thermometer but it is called thermoscope.

What is Thermoscope ?

Thermoscope is predecessor to thermometer. In an easy term, it is called thermometer without scale. Thermoscope is an instrument used for detecting difference in the temperature only. It only gives information about whether the temperature is higher or lower or similar.

1612 Thermometer

Santorio Santorio, an Italian inventor, became the first person to put scale on the Thermoscope. So the inventor of thermometer is thought to be Santorio Santorio but thermometer was very rudimentary. It was perhaps the first crude clinical thermometer, as it was designed to be placed in a patient's mouth for temperature taking.

1654 Liquid-in-glass Thermometer

In 1653, the first enclosed liquid In glass thermometer was invented by Grand Duke of Tuscany, Ferdinand II. He used alcohol as liquid in the thermometer. But it was still inaccurate and didn’t have a measurement scale. But the man credited with using the freezing point of water as the "zero" or starting point was a Londoner, Robert Hooke, in 1664. An astronomer called Roemer in Copenhagen chose ice and the boiling point of water as his two reference points, and started keeping weather records, but there were still uncertainties about how to devise an accurate scale that would be reliable everywhere.

 

1714 Mercury-in-glass Thermometer

Generally a Mercury-in-glass thermometer is called mercury thermometer. In 1714, a German instrument maker, Dante Gabriel Fahrenheit invented mercury-in-glass thermometer for the first time. He used mercury as the expanding fluid because mercury is a liquid metal that expand uniformly over normal temperature ranges and contract at lower temperature without sticking at side of glass tube.

In mercury thermometer, it consists of a bulb containing mercury attached to a glass tube of narrow diameter; the volume of mercury in the tube is much less than the volume in the bulb. The volume of mercury changes slightly with temperature; the small change in volume drives the narrow mercury column a relatively long way up the tube. The space above the mercury may be filled with nitrogen gas or it may be at less than atmospheric pressure, a partial vacuum. Mercury in a small glass bulb expands into an evacuated, linear, uniform cross-section glass tube. Here the amount of expansion is used to measure the temperature of bulb.

In 1724, he introduced the standard temperature scale that bears his name—Fahrenheit scale—that was used to record changes in temperature in an accurate fashion. He introduced three fixed point and 8 graduations. Zero degree was the lowest temperature that he could obtain in laboratory, the temperature of mixture of water, water ice and ammonium chloride. 32 was the temperature  of an ice and water mixture, 96 was the temperature of human body.

  

1867 The first medical Thermometer

The first real medical thermometer was invented by Sir Thomas Allbut in 1867. It was six inches long and took about five minutes to take a person’s temperature.

For almost a hundred years thermometers were basically unchanged. They contained alcohol or mercury and were considered to be very accurate. More modern thermometers were developed after World War II that used infrared technology and placed in the ear. They utilized tiny electrical circuits and numerical readouts  that could measure temperature more quickly and with more precision than the liquid filled glass tubes. Today modern thermometers use some type of electrical sensors to measure temperature but the same numerical scales developed in the 1700’s by Fahrenheit and Celsius are still being used.