1724: Fahrenheit scale - The book of science

Fahrenheit scale
Frigorific mixture
Recalibration
Commentary

Fahrenheit scale

In 1701, Isaac Newton described a temperature scale
in which zero was the freezing point of water
and twelve was the human body temperature.
Daniel Gabriel Fahrenheit was a glassblower
who made barometers, altimeters, and thermometers.
He invented the mercury-in-glass thermometer in 1714.
He met and took ideas from Ole Rømer for his own scale.
Fahrenheit originally established
three calibration points for his scale.
He set ninety six at the human body temperature;
he set thirty two at the freezing point of water;
and he set zero at the temperature of a mixture
of ice, water, and ammonium chloride.

Frigorific mixture

A mixture of equal amounts
of ice, water, and ammonium chloride
is a frigorific mixture. Together, these ingredients
reach a stable temperature
regardless of their initial temperatures.
But something was wrong with Fahrenheit’s mixture;
maybe the salts were impure or poorly dissolved;
it didn’t work quite right.

Recalibration

Fahrenheit chose ninety six for body temperature
to improve the simplicity of his scale.
He started with Ole Rømer’s scale,
but he didn’t like that water freezes at 7.5 °Rø
or that body temperature is 22.5 °Rø.
He multiplied Rømer’s degree by four,
separating the freezing and boiling points by sixty degrees,
but he wanted a difference of sixty four
to make it easy to mark out the degrees
using a compass to bisect the distances,
so freezing became thirty two
and body temperature became ninety six.
Today the Fahrenheit scale
is defined in reference to the Celsius scale,
which is calibrated by any two of sixteen
reference points—the vapor point of helium,
the melting point of gallium,
the triple or freezing points of various elements,
and the triple point of Vienna Standard Mean Ocean Water.
Water freezes at 0 °C or 32 °F,
and boils at 100 °C or 212 °F.
Today the United States
is the only English-speaking country
for whom the majority of citizens
a balmy temperature of 25 °C doesn’t signify.

Familiarity breeds more than discomfort with change. Without thinking, one loves it, like family, without control, without consideration of deservedness.