Daniel Gabriel Fahrenheit physicist, inventor and scientific instrument maker was born #OTD in 1686.
He created the temperature scale that bears his name in 1724. He set the zero point of his scale at the temperature of a mixture of ice, water, and ammonium chloride, a freezing brine solution. He established 32°F as the freezing point of water and 212°F as the boiling point of water at standard atmospheric pressure. He also invented the mercury-in-glass thermometer.
French physicist Jean-Pierre Christin published the design of a mercury thermometer using the centigrade scale with 0 representing the melting point of water and 100 its boiling point.
Available at : Annales des sciences physiques et naturelles, d'agriculture et d'industrie
By Société d'agriculture, sciences et industrie de Lyon. via @googlebooks
In his paper Observations of two persistent degrees on a thermometer, Christin recounted his experiments showing that the melting point of ice is essentially unaffected by pressure. He also determined with remarkable precision how the boiling point of water varied as a function of atmospheric pressure. He proposed that the zero point of his temperature scale, being the boiling point, would be calibrated at the mean barometric pressure at mean sea level.
Historical note:
1742 Anders Celsius invented the Celsius temperature scale. In its original form the scale had 0 degrees for the boiling point of water and 100 degrees for its freezing point.
1743 The scale was changed by Jean Pierre Christin so that 0 degrees is the freezing point of water and 100 degrees is its boiling point.
Anders Celsius published his research at Abhandlungen über thermometrie, von Fahrenheit, Réaumur, Celsius, (1724, 1730-1733, 1742)
Hrsg. von A.J. von Oettingen.
Swedish astronomer, physicist, and mathematician Anders Celsius died #OTD in 1744.
In 1742, Celsius introduced the temperature scale that bears his name. His original scale was actually the reverse of what we use today: it set the boiling point of water at 0 degrees & the freezing point at 100 degrees. However, shortly after his death, the scale was reversed by Carl Linnaeus, resulting in the 0 degrees for freezing & 100 degrees for boiling that we are familiar with.
A pioneer of exact thermometry, he helped lay the foundations for the era of precision thermometry by inventing the mercury-in-glass thermometer and Fahrenheit scale.
According to Fahrenheit's 1724 article, he determined his scale by reference to three fixed points of temperature, namely 0, 30 and 90 °F respectively. via @wikipedia