Daniel Gabriel Fahrenheit (/ˈfærənˌhaɪt/; German: [ˈfaːʀənhait]; 24 May 1686 – 16 September 1736) was a Polish/Dutch physicist,engineer, and glass blower who is best known for inventing the mercury-in-glass thermometer (1714), and for developing atemperature scale now named after him.
Fahrenheit Scale :
According
to Fahrenheit's 1724 article, he
determined his scale by reference to three fixed points of temperature. The
lowest temperature was achieved by preparing a frigorific mixture of ice,
water, and ammonium chloride (a
salt), and waiting for it to reach equilibrium. The thermometer then was placed
into the mixture and the liquid in the thermometer allowed to descend to its
lowest point. The thermometer's reading there was taken as 0 °F. The
second reference point was selected as the reading of the thermometer when it
was placed in still water when ice was just forming on the surface This
was assigned as 32 °F. The third calibration point, taken as 96 °F,
was selected as the thermometer's reading when the instrument was placed under
the arm or in the mouth.
Fahrenheit
came up with the idea that mercury boils around 300 degrees on this temperature
scale. Work by others showed that water boils about 180 degrees above its
freezing point. The Fahrenheit scale later was redefined to make the
freezing-to-boiling interval exactly 180 degrees, a
convenient value as 180 is a highly composite number,
meaning that it is evenly divisible into many fractions. It is because of the
scale's redefinition that normal body temperature today is taken as 98.2
degrees whereas it was 96 degrees on Fahrenheit's original scale.
The
Fahrenheit scale was the primary temperature standard for climatic, industrial
and medical purposes in English-speaking countries until the 1960s.
