Degree Fahrenheit

Thermometer with main scale of Fahrenheit and secondary scale in Celsius degrees

The degree Fahrenheit (represented as °F) is a temperature scale proposed by German-born Polish physicist and engineer Daniel Gabriel Fahrenheit in 1724. The scale states as the freezing and boiling temperatures of water, 32 °F and 212 °F, respectively. The definition method is similar to that used for degrees Celsius (°C).

"Locating the thermometer in a mixture of ammonium salt or salt water, ice and water, I found a point on the scale I called zero. A second point I got it the same way, if the mixture is used without salt. Then I denote this point as 30. A third point, designated as 96, was obtained by placing the thermometer in the mouth to acquire the heat of the human body».

History

There are a few versions of the story of how Fahrenheit came to have that temperature scale. According to Fahrenheit himself, in the article he wrote in 1724, he determined three temperature points. The zero point is determined by placing the thermometer in a mixture of ice, water, and ammonium chloride. This is a type of refrigerant mix, which stabilizes at a temperature of 0°F. The alcohol or mercury thermometer is then placed in the mixture and the liquid in the thermometer is allowed to reach its lowest point. The second point is at 32°F with the ice and water mixture, this time without the ammonium salt. The third point, 96 °F, is the level of the liquid in the thermometer when it is held in the mouth or under the arm (in the armpit). Fahrenheit noted that using this scale, mercury could boil close to 600 degrees.

Another theory is that Fahrenheit set 0°F and 100°F on the scale by recording the lowest temperatures he could measure and his own body temperature, while in a slight feverish state. He took the lowest temperature that was measured in the harsh winter of 1708 to 1709 in his city of Gdansk (Poland), near –17.8 ° C, as point 0 ° F.

A variant of this version is that the mixture of ice, salt and water recorded on the Fahrenheit scale was obtained in his laboratory and the highest was taken from his body temperature at 96 °F.

Fahrenheit wanted to abolish the negative temperatures that the Rømer scale had. He set his own body temperature at 96°F (although the scale had to be recalibrated to normal body temperature, which is close to 98.6°F, equivalent to 37°C); he divided the scale into twelve sections and subsequently each of those sections into 8 equal subdivisions, which produced a scale of 96 degrees. Fahrenheit noted that on this scale the freezing point of water was 32°F and the boiling point was 212°F.

Conversion to other units

The different possible conversions, among them to degrees Celsius, degrees Réaumur, Rankine and Kelvin are:

Fahrenheit temperature conversion formulas

From	a	Formula
Fahrenheit	Celsius	C=(F− − 32)/1,8{displaystyle C=(F-32)/1,8!}
Celsius	Fahrenheit	F=1,8× × C+32{displaystyle F=1,8times C+32,!}
Fahrenheit	Kelvin	K=(F− − 32)/1,8+273,15=(F+459,67)/1,8{displaystyle K=(F-32)/1,8+273,15=(F+459,67)/1,8,}
Kelvin	Fahrenheit	F=1,8(K− − 273,15)+32=95K− − 459,67{displaystyle F=1,8(K-273,15)+32={frac {9}{5}K}-459,67,!}
Fahrenheit	Rankine	Ra=F+459,67{displaystyle Ra=F+459,67,!}
Rankine	Fahrenheit	F=Ra− − 459,67{displaystyle F=Ra-459,67,!}
Fahrenheit	Réaumur	Re=(F− − 32)2,25{displaystyle Re={frac {(F-32)}{2,25}},!}
Réaumur	Fahrenheit	F=(2,25)Re+32{displaystyle F=(2,25)Re+32,!}

Fahrenheit grade conversion formulas

From	a	Formula
Fahrenheit	Celsius	C=F1,8{displaystyle C={frac {F}{1,8}}},!}
Celsius	Fahrenheit	F=1,8C{displaystyle F=1,8C,!}
Fahrenheit	Kelvin	K=F1,8{displaystyle K={frac {F}{1,8}}},!}
Kelvin	Fahrenheit	F=1,8K{displaystyle F=1.8K,!}
Fahrenheit	Rankine	Ra=F{displaystyle Ra=F,!}
Rankine	Fahrenheit	F=Ra{displaystyle F=Ra,!}
Fahrenheit	Réaumur	Re=F2,25{displaystyle Re={frac {F}{2,25}},!}
Réaumur	Fahrenheit	F=2,25Re{displaystyle F=2,25Re,!}

Note the difference between temperature conversion (temperature of a body is 180 °F = 82.22 °C) and degree increment conversion (temperature of a body has increased by 180 °F = 100 °C).

Use

This scale was used in most Anglo-Saxon countries and Puerto Rico for all types of use. Since the 1960s, various governments have carried out policies aimed at adopting the international system of units and its use was displaced. However, the measure is still used in the United States and in certain very rigid industries, such as oil.^{[citation needed]} In addition, this scale is used in weather and gastronomy reports.^{[citation required]}

For scientific use, an absolute scale was also used, the Rankine scale, which set 0 to absolute zero in a similar way to what happens on the Kelvin scale.

History

Daniel Gabriel Fahrenheit (1686–1736) proposed his temperature scale in 1724, basing it on two temperature reference points. On its initial scale (which is not the definitive Fahrenheit scale), the zero point was determined by placing the thermometer in "a mixture of ice, water, and salis Armoniaci [translation ammonium chloride] or even sea salt"[12] This combination forms a eutectic system, which stabilizes its temperature automatically: 0 °F was defined to be that stable temperature. A second point, 96 degrees, was approximately the temperature of the human body. A third point, 32 degrees, was marked as the temperature of ice and water "without the salts mentioned".

According to a German story, Fahrenheit actually chose the lowest air temperature measured in his hometown, Danzig (Gdańsk, Poland), in the winter of 1708-09, as 0 °F, and only later had the need to be able to make this value reproducible using brine.

According to a letter Fahrenheit wrote to his friend Herman Boerhaave, his scale was based on the work of Ole Rømer, whom he had met earlier. On the Rømer scale, brine freezes at zero, water freezes and melts at 7.5 degrees, body temperature is 22.5, and water boils at 60 degrees. Fahrenheit multiplied each value by 4 to eliminate fractions and make the scale finer. Next, he recalibrated his scale using the melting point of ice and normal human body temperature (which were 30 and 90 degrees); he adjusted the scale so that the melting point of ice was 32 degrees, and the body temperature 96 degrees, so that 64 intervals separated the two, allowing him to mark degree lines on his instruments simply by bisecting the 6 interval times (since 64 = 26).

Shortly thereafter, Fahrenheit observed that water boils at about 212 degrees using this scale. The use of the freezing and boiling points of water as fixed reference points for thermometers was popularized by the work of Anders Celsius, and these fixed points were adopted by a committee of the Royal Society led by Henry Cavendish in 1776. Under this system, the Fahrenheit scale was slightly redefined so that the freezing point of water was exactly 32 °F, and the boiling point was exactly 32 °F. exactly 212 °F, or 180 degrees more. For this reason, normal human body temperature is about 98.6°F (oral temperature) on the revised scale (whereas it was 90° on Rømer's Fahrenheit multiplication, and 96° on his original scale)..

On today's Fahrenheit scale, 0 °F no longer corresponds to the eutectic temperature of ammonium chloride brine, as described above. Instead, that eutectic is at about 4 °F on the final Fahrenheit scale [note 2].

The Rankine temperature scale was based on the Fahrenheit temperature scale, with its zero representing absolute zero instead.